You really need to look at the pistons and heads to make sure you have enough compression. Some 383 pistons will give you extremely low compression especially on a 906 head.

Don't ask me how I know........

67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......