The owner is correct, that is an AMC 327 in there. A good torqy motor, but not compatable with the later engines or transmissions. I've got one in my '60s ski boat- originally converted by Graymarine. For converting a CJ, a later V8 swap is bolt-bolt in with factory or aftermarket parts, which would be much easier than fooling with a 35 year old motor with custom adapters and limited parts availablilty.
1985? Jeep CJ-7: 360, 999, D300, LOMAX 4:1, Dana 44s, 4.10's, Aussies front & Detroit rear. S0A, York OBA, YJ tub, 36" IROKs-
1989 YJ Sahara: 258, puko tranny, np231. 2-3" spring and 2" body lift. 33" TSLs- latest project.