ahhh, what a question
Th easiest way would be to hand it over to a workshop along with an arm and a leg (possibly a kidney) and let them deal with everything. But where's the fun in that?
Obviously you're going to need a manual gearbox (I have read about a u13 attesa with a gti-r gearbox, but I don't know if it was a straight swap or not) IMO the best place to get this is either from a whole wrecked manual u13 4wd bluebird (sr20de or sr20det engined) or from a front cut - maybe ask around the pulsar forums as they frequently import front cuts just for the engine and usually sell off the gearbox. In both these cases you'll have all the parts needed for the conversion.
From my research I can tell you the following with some degree of certainty:
- The front gearbox mount is different from auto-manual
- The gear shifter linkages are unique to the u13 attesa
- You'll need a s14 clutch, and gti-r throwout bearing
- The drive shafts should not be an issue
- Parts such as the gear shifter and interior surround panel can be sourced from the aus-spec u13 if required
- You can retain your auto ECU - simply unplug the separate auto transmission computer
Then there are a few bits and pieces which are debatable:
- Some say that you need to change the rear diff from auto-manual, however if I understand correctly you can bolt the auto transfer case to the manual gearbox and that'll all be sweet
When it comes to the actual conversion I understand that the best method is to lower the engine/gearbox as one from the car (not pull them out through the bonnet) then separate the auto box and bolt on the manual. Then bolt on clutch related parts etc, bypass the auto inhibitor switch, figure out how to wire the reverse lights and away you go!
If you have any specific questions please feel free to ask away!