I can field this one for you.
If you've got a MK.II S12 it's pretty straight forward (1987 - 1988). Use the Stock Transmission on the S12. it will bolt up to the CA18DET.
If you want to use the S13 transmission you'll need the first part of the S13 driveshaft, you'll need to make a new transmission mount, and also cut the shifter hole about 2 inches back.
Wiring is pretty straight forward if you have the full harness. The only major difference is how the fuel pump is wired up, so do some research on that.
for more info, check our hybrid forum over at
http://www.club-s12.org
one of our members did a writeup.