I've found a 230TE manual. Just wondering if a 617 will accept the flywheel, transmission. I'd like to convert this wagon to diesel if possible. Although, I'll most likely just drive it as is for a while and pretend.

Is it THAT rare?

do a search, there are several rather large 4-speed swap threads back there. I believe the answer is yes, but some of the parts are tricky to find.
Heck, probably are threads on switching the engine from gas to diesel as well.

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1971 220D/4-speed ~250K mi. Family owned (dads side) through three generations since <5K miles.
1992 Chrysler LeBaron, 3.0V6 125K. Family owned (moms side) through three generations since new.
1977 Chevy Camaro Continual hotrod project
1970 Cadillac Sedan DeVille 472ci and nearly 19' long
1974 Fiat Spider Still needs work