The car came with a complete 320i drivetrain. So all the hard work of a 5 speed conversion was already done!

Specifications

5 speed 320i Gertrag 245 transmission (stock shifter linkage)
215mm clutch
320i clutch slave cylinder
E12 motor mounts
320i transmission mount (Urethane Transmission Mount)
3.91 LSD w/ stock 25% lockup
Redline MTL in the tranny and Redline diff fluid

Chart for Getrag 245 with 3.90 differential. Dyno runs should be done in 4th since ratio is 1:1

A while back I had a chance to buy a Quaife Differential and I bought it at a great price

Unfortunately I hit some hard times and had to sell it! It would be great for auto-x. This is still something I might purchase down the road once again. The only bad thing about the Quaif that I heard is that it does generate a lot of heat and it will turn into and open differential if one of the wheels comes off the ground. Otherwise it transfers all the power to the wheel with the most grip and is awesome. I also heard that they are a pain to install. So maybe someday, but its not a simple thing.