I switched from the Ford 3 Speed to a Muncie.
I kept the bellhousing, crossmember, and Driveshaft, but I had to change the front yoke, which was no big deal. I don't remember if the clutch was different, because I bought a new one for the swap- you should at least change your disk anyway while you have it apart.
Overall its very easy. However, if you have a console, not that it may be hard to get a modern shifter into the console- you may have to use an original, which are pricey.