I like your T25 idea Reubes, 220kw at the treads on a 300 with 14psi safe tune and reliable,
so halve that, bingo,they are well priced to buy from the Z boys...they upgrade to hks2530's if they are smart, or fuk about with disco potato's for an upgrade...
I have had pairs for free and $50 in the past, (quite a while ago)
you can upgrade to BB cartridge in the future..

The disco potato is just slang for a turbo from an S15 sentra. (GT28)
Its just one of those strange things. According to legend, the car looks like a potato?? and it originally had that colour shifting paint, hence disco.
Here is a link that apparently explains it...
http://www.modified.com/projectcars/0306scc_project_nissan_silvia_part_2/

As for stiffening up, well to be honest I haven't really thought about that. I don't expect to have any chassis twisting issues. Its going to be a great upgrade, but nothing that warrants seam welding I would have thought. I don't have shock towers to run a strut brace, although I could Fab something up similar I spose.

And since the car is a half ladder chassis half monocoque design, there isn't a chassis to strengthen as such.

As for passing 150+hp, You may be right. I don't really know what to expect. I'm aiming for 130-150hp, but if I can get more and keep it streetable/reliable, then sure, bring on the ponies! I'm just trying to keep it sensible and achievable. More ponies in the future are always an option one I have the car all sorted out.

To be honest, I reckon if I went all out crazy and really lent on the motor, I'm sure that 250+hp is possible, but I don't think that it would be that useable or reliable. Mostly a dyno pony in the end, which is pointless in my opinion. Plus, I don't think a A-series bottom end would hold up to mega boost for too long.
I also don't have a secret money tree in the backyard to make that happen either.

If this mod is a success, then perhaps the next version can be a mad as mad version to see what can be squeezed from an a-series block. (now where is that money tree???)

Ok, so piston options for the mazda conversion.
 

Basilcally the current situation is that I have a a15 block already bored out to 77mm with new pistons.
 
If I can use this block, then it means less machining costs for me now.
I do have access to another block that is good to go for machining, but thats extra cost.
 
I have also been looking at piston options.
These for example are pretty close to the std a15
http://realstreetperformance.com/Products/CP-Pistons/CP-Forged-Pistons-Mini-Cooper-S-Prince-1-6L-77mm-9-51.html
 
The std a15 pin height is 30mm
These mini cooper forgies have a pin height of 1.121 inches (28.47mm by my calculations). Thats 1.53mm lower, which would lower my compression, which cant be too bad for a turbo/efi setup.
 
Or these motorbike pistons
http://www.ebay.com.au/itm/Wiseco-Forged-Piston-Kit-77mm-12-7-1-Comp-Fits-01-04-Yamaha-WR250F-/360961567814?pt=Motorcycles_Parts_Accessories&hash=item540afc6c46
There are plenty of options on fleabay to choose from and at around $150 per piston isnt too bad considering what a set of "datsun" forgies will cost you well over $1000.
 
 
Or these from PeterZerket.com
http://www.peterzekert.com/for-sale/engine/engine-components/136-new-datsun-a-series-race-pistons-usd-700set-of-4

A15
head cc's - 29-31cc
compression ratio  - 8.5:1
pin height - 30mm
 
Mazda B6T
head ccs - ??
compression ratio  - 7.9:1
pin height  - ??
 
Is there a way to work out the expected compression ratio from this amount of information?
 
Running with the mini pistions means that it is 1.5mm lower in the bore. How much this would drop the compression ratio i dont know. 7.9:1 compression is pretty low and is probably low enogh for a turbo application already.

Rob had a head that he had done a heap of work to already. Its got all the neccessary holes plugged and the others notched to allow the right water and oil flows.
 
Im not sure what the head is from but I suspect that its from either a Ford Laser TX3 or a mazda 323 turbo as it came with an intake that wraps over the head, unlike the front pointing MX5 intake.
It looks like this one
http://us1.webpublications.com.au/static/images/articles/i29/2921_6lo.jpg
 
I spose the right thing to do is post some pics.... too late now, and i dont think Ill have enough sunlight tommrrow for pics. Next day perhaps.
 
Just found these pistons
http://www.summitracing.com/int/parts/uem-9127h-1-0mm/overview/
 
As for pistons, im not fussed really. If i can get some forgies cheap enough, then ill run with those, else Ill use the 77mm units I have now and ceramic coat them and combustion chamber to suit. Add the lubrication treatment to the edges and bobs your uncle. Still to get quotes on that work for a price comparision.

I think the B6T is 78mm bore
32mm pin height
20mm pin

Pics finally uploaded
But I cant seem to insert any into the post  . Working fine in Google Chrome. Wont work in Explorer.

Lightened flywheel ready to go
 

Assortment of goodies needed fro the mazda conversion
Bottom is the custom head gasket
next up is the new wheel for the cam shaft to run the oil pump
New timing belt
Adjuster and tensioner pulley
Modified Datsun crank pullet to drive it all.
 

Photo of the underside (Piston 1 & 2) showing which oil/water galleries have been plugged and which have been drilled.
 

Photo of underside (Piston 3 & 4) showing which water and oil galleries have been plugged and drilled
 

Photo showing head with intake bolted on. As you can see the intake wraps over the top, which makes me think its from a mazda 323 or Ford TX3 turbo.
 

Photo of the T25 turbo from a 300zx. Ive just realised that I dont think I can use the factory dump pipe as the turbo faces the wrong way. Once I get an exhaust manifold ill check for mounting. If I can use the std dump pipe, its just cheaper, and i believe that you can port the hell out of it for flow.
 

Photo of whole head. Should be able to see all the plugs and drill spots.
 

This shows the oil drains ready to go in the head. These will need to run back to the sump, along with the turbo drain. Not sure Iif I can get away with joining them up near the sump so i only have one pipe/hole in the sump.
 

H-beam rods (A15 length rods with 20mm wrist pin), front timing plate and seals for crank and cam shaft.
 

Exhaust port side of Mazda Head
 

Intake side of Mazda head

is that good enough mr Dundee!!

Just spoke with a ceramic coater here in Perth
Prices quoted as follows. All are per item plus GST
Piston top and sides - $55
Cylinder head
Chambers - $50
exhaust port - $11
intake port - $11
valves - $11

Isotropic polishing of crank - $450

That gives me a total $644 +gst for the head and pistons, and $450 for the crank+gst = $1203.40 inc.

These guys can ceramic coat anything and claim that they regularly do it for all sorts of performance applications (eg drag cars) as well as engines that need extreme reliability (eg power station engines).

The guy I spoke with wasn't very good at explaining things to me. I asked a few curly questions and he wasn't able to answer them, but that doesn't discount its value. Its just that he is not a good sales person rather than a shady dealer.

Painting the inside of the block was also mentioned to me by another person. From what I've read in the interwebs, its serves very little purpose in modern engines (ie anything with cast iron). Its apparently was used to help seal up old aluminium blocks as they leaked through the walls and it helped with oil return back to the sump.

Modern cast iron (anything Datsun) doesn't leak thru the walls.
And if the extra 100ml of oil that isn't returning as fast means you engine goes bang, then there is something else to worry about. A dry sump setup, windage plates, knife edge crank, or anti-slosh gates in the sump would be a better option I would think to keep the engine oil fed.

I have a couple of those crank scrapers and windage trays for my up coming projects
Can show them to you sometime so you can see them in the flesh
 
Also dry sump pans etc
 
I just need your coupe shell , some more money  and one of those head conversions