I believe the AVS debuted in 1968, so anything before that is probably an AFB. Not much difference though in rebuilding it.
Carter AFB useage
1962 318 poly, 361-B, 383-B, 413-RB
1963 361-B, 383-B, 413-RB
1964 273-A, 361-B, 383-B, 413-RB
1965 273-A, 383-B, 426W-RB
1966 273-A, 383-B, 440-RB
1967 273-A, 383-B, 440-RB
Carter AVS useage
1968 340-A, 383-B, 440-RB
1969 340-A, 383-B, 440-RB
1969 340-A, 383-B, 440-RB
1970 340-A, 383-B, 440-RB
1971 383-B, 440-RB