Hi guy's.  So I'm having a serious thought about possibly building up an A15 and 5 speed combo for the new dat 1000. Anyone have any advice on fitment isses? I already know that I need to fab up some off set engine mounts. my main concern is the fitment of the 5 speed box? or are there any other engine box conversions out there where I don't have to do tunnel mods. would love a g13b but looks like the tunnel needs cut...
Any help would be much appreciated. cheers!

Cheers Neil, yeah I think I might just stick with an A Series engine as I don't really want to touch the body of the car. wouldn't mind taking my time and having a shot at an A series twin cam head swap for something different, make it cross flow and get the most I can out of it. 
I found a complete and possibly running A15 for $600 would you say it's worth it? cheers again 

<----- what he said,
Big blocks make the Thou a great thing,
gearbox and diff depending on how hard you want to treat it... 

A series 5 speeds aren't that strong if you build a hottie
 
All A15's should be oval ports

Thats what I did
3 gearboxes and 2 diffs later

After owning many A15s in several guises Im a true believer in the early A12 with 76mm bores
they rev higher and a good 4 speed puts up with them as does a 3.45 sourced from DD on 1200.com
That ratio was available for h150 and H165 and keeps the revs at a nice level for the 4 speed
If I going turbo you need to engineer it so would go straight for A15 capacity to get early spooling.
Otherwise no engineering you can pick up an A12 for biscuits and H89 head and GX cam.

Metal worker! great as Im not and still made effective bike carb manis
that totally woke up any A series regardless of their steed even stock.
Honda Keihins worked well and looked old school from old cb1000.
A12s are underrated, just opening up the round ports, mild cam,
A15 sunny stock cast header or aftermarket, elec ignition and bike carbs
produce better torque than a A12 GX motor lower where it counts and
can rev out very nicely especially with 76mm pistons giving less shrouding.
The oval heads are usually for more hp at the top but not in the mid range.
This was confirmed by rallye guys in Victoria that campaigned a 1200, 120y
and a sunny 310 and swore the round ports with L16 valves went better
for midrange and helped better in all areas of the curve.
The bike carbs around 36mm are all you need and sound very sweet.
You can also fit the A14 crank into your A12 and have close to 1400cc
without worrying about engineering or your gearbox. The rod stroke ratio
is even better for the street and revs very nicely still with 78mm stroke.
An old member had the hybrid A12 with A14 crank, opened up A12 rods,
A15 pistons milled 1mm off the tops and was his favorite daily engine
and weekend getaway hills and curves setup. The rods are lighter on
the hybrid than an actual A14 121.5mm vs 133mm, pistons are lighter
again 28.5mm vs 34mm comp height and shorter rod ratio welcome
higher comps with less issues than traditional longer rod ratio setups.

supposedly speedway guys have done them for class rules so they can get away with more capacity
eg 1070cc vs 9xxcc
Rob where one of our members here got the twin cam head setup was doing up a 1000 tudor
with an 8v ohc mazda head and I think the 16v soch is a better idea !
simple small light and rev happy whats not to like! I reckon go for it as the power increase is massive.
quad carbs sound awezum no matter the brand as long as set up properly but I loved the lil keihins!
everyone used to think my A series where rotary engines as they buzzed like crazy