Not a bad ideal. Unless someone has attempted this before I imagine it is an unknown senario. One thing might be to compare the casting numbers on the two forward cases. If the same it greatly increases the possibility in my opinion. Of course with the belhousing cast with the forward case and the starter hump on the opposite side the numbers unfortunatly will be different.

Or if the two case numbers are found to be otherwise interchangeable. A question on the german site might bear fruit as really there have been a lot more manual transmissions in europe.

Another thought is the ideal of cuting off the starter hump and moving it using an alignment jig. Perhaps not too difficult if otherwise the bellhousing is the same. Basically if all the holes lined up with the jig and the surface was flat it might work well. All that might be required then is a piece of steel with all the belhousing bolt holes for the bolts drilled out. This of course from the 616-617 belhousing flange. You could start out with a paper pattern of the holes locations for comparison. At least that might show if moving the hump it is remotely possible.

Bolt the cut off hump to the plate with the later bellhousing and weld away if otherwise simular. Good thinking of you to think of a possibility as I too really want a five speed for one of my 240s. This is the kind of thing that can be missed by people quite easily. Usually turns out impractical but not always. Keeep us informed if you even just try the hole matchup senario or find case interchangability information.

It is quite possible they just for our purposes might have changed only the bellhousing part of the casting. It would have cut tooling and production part costs down on internal parts. Another way to check this out is to compare internal part numbers in both cases from manuals.

If the exact same part numbers you have your answer. Perhaps one of our members has the internal part numbers for both transmissions parts?