There are Jeep/AMC sixes everywhere, many sources for a rebuilt. IIRC many came stock with AMC style Torqueflites. The 258 was carbureted into the '80s. They used the A-998 from 1972 thru 1987 behind the 258 carbureted motor. These Torqueflites use an AMC-specific case but are all Chrysler inside.

Think Gremlin or Pacer.

Heck, the Pacer kind of looks like the '50 Nash!

R.