Isn't the output shaft different on the RV transmission, flanged instead of a slip yoke?
In order to change the output shaft the trans needs complete disassembly.
Pretty sure that is only true of the big "class a" stuff. The smaller "van nose" types are pretty much slip yoke
Other thing you need to watch out for in the big stuff is the -3 engines which can be much different, esp. 413/426 with the oddball heads/ intake/ exhaust. What you essentially have with them is a block, crank, and "I guess" rods
