A small block 400 is a step too far. Even with "steam hole" heads, they had chronic overheating problems and the rod/stroke ratio was way wrong for good torque. Other than a few applications in big station wagons, motorhomes, and trailer towing pickups, it was a solution looking for a problem. Anything a 400 could do, a big block could do better, be it a 396, a 427, or a 454. 383 was never a factory engine size- - - -the hotrodders invented that one.
Jerry