no need to change the clutch. I swapped out a GP 4 speed for an ACN 5 speed. It was a rabbit motor that I installed into a jetta using the gasser's original transmission. took the motor/tranny out, unbolted the shatty gas engine, and the ACN slipped right on to the 1.6. and on a side note, I think caddies have 90 mm axles. 100 mm axles only came on things that had 16v motors, I thought.