BMW 750 V12

A six speed box from an 850CSi will fit. I THINK this is the same box as used on the E34 M5 3.8. You'd also need the flywheel as auto/manual flywheels are different.

You will also need a clutch pedal, new brake pedal, new engine management (probably), alterations to the transmission tunnel etc. etc.

The chances are it will not work, and I can't see how the cost involved can be worth it on such an old car.

There were a [very] few E32 735i / 735iL (for chauffeur driven) around with manual boxes from introduction in the late 80's to ~1992 - look for one of those. The current E63 645i has an optional 6 speed box, and there are a few of those.

In the 1980's I had a couple of E23 735i manuals, and they were a sparkling drive out of town, but hard work within it.

Nope. Bell housing is different.

The only trans you can use is from an E31 850, up to the end of 1994 production for 850i and 850Ci, or one from an 850CSi.

Brett Anderson KMS