I have a B20 ute i bought off ebay for 800 a few weeks ago. Have resprayed it and re-wired  it (im an auto elec) and now im doing the brakes. Its all standard atm and i have replaced the rear slaves with new ones. i bled the system when i fitted the slaves and the brakes seemed to half work. after leaving it for a couple weeks, the resevoir is empty, pedal goes to the floor and cant find any wet patches anywhere. pretty sure it had too much fluid in it to self bleed and empty the resevoir so im not sure whats goin on there. 
 
Anyway if 120y disk go on the front easily, then ill just head to the wreckers and have it all over and done with.
Can anyone shed any light on this??

I have fitted Datsun 1600 disc brakes to my mates 1000, I had to modify the caliper mounting plate and also had to do a small amount of machining to the hub to fit the rotors. I will be not be able to post any pictures until my mate come back from North America.
I seem to remember that it was not a hard job to do, we had to use the brakes from a car pre 1968 Datsun.
 
 
Alan

It was quite a few years ago and I cannot remember all the details, I think I machined the inside of the rotor and the outside of the  std 1000 hub to reduce the radius on the hub. We then used a 9/16" bore twin master cylinder I think from a 120Y. With out a booster, the brakes worked very well with good pedal feel.
 
Alan.