I reckon the bore is way too small for a stroker 383?
When you fit decent 'BIG VALVE' heads on, the valves are badly shrouded before you start!
I have the same set up with a 400 block, biggest bore in a low deck deck screamer...
Pistons and rods off the shelf no drama's lol...
The car in the avatar had a 400 block done by Koffels.
547 cubes and made 900hp with Indy heads on pump gas...