[mr48chev]

You need the Taskforce bellhousing and a 54 Crossmember makes things simpler although you can do a couple of mods to the 50 crosmember to get the mounts to fit.

Edited because I assumed rather than totally read the question the other night.

When I bought my 48 in 1973 it had a 194 Chevy II six and Cast iron V8 bellhousing and the stock 3 speed that jumped out of second gear. All I know about the crossmember mods is that they had done some torch and stick welder modification to it. Basically set the bellhousing with mounts on the crossmember and figure out what mods you need to make and do the changes. The job will be more tedious than hard. It wouldn't have been hard for me when I was 27 and getting the truck ready to go to the 1973 NSRA street rod Nationals in Tulsa but now at 77 sitting under the truck cutting and welding on the crossmember would be a challenge.

You should be able to make a pattern off the V8 bellhousing and mounts that you can hold up against the crossmember for a basic idea.

Use the stock clutch linkage including the fork.

Front mounts are your choice and I think that there are mounts that work with that crossmember pretty well. They shouldn't be that hard to fabricate if you are up to the fabricating. That calls for show and tell photos from the folks with the M II front ends showing and telling how they did their small block mounts or where they got them.