Another option to finding a complete used motor is buying a stroker rotating assy for the 383 block, and putting some nice heads on it.

.040 over is a 491, .060 over is a 496..... both using a 4.250 stroke.

68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads