Pretty much. You can turn the 5.125" bearing retainer down to 4.8, and open a 4.35 bell up to 4.8 without causing too many issues, or buy the 4.8" retainer with the 4.16" bolt pattern and again open up the bell to 4.8", but either way to have to machine the bell.
Only way around some kind of machine work is to find a SB bell with a 4.8" register (good luck) or buy an OD bell. F-bodies at the junk yard is one way to find the OD bells, or some of the early model 1/2 ton trucks that had 833 OD's. But even those are getting hard to find at the yards.
I could use one myself, although I'm not going to be needing it in the immediate future so I'll probably just keep an eye out at swap meets until then.
