The heads are supposedly stock, which would be close chambered 516 or 916 castings if I'm correct. The stock 2 barrel engine was rated at 270hp, 4 barrel at 325hp. It does have dual exhaust now, with factory manifolds. 383-2 was rated 9.2:1 compression, 383-4 was 10.0:1.
Fender tag says its a...