I figure a tenth is waaaay out there, but thought I'd ask. The shop did sonic check my engine blocks, so perhaps they can do the deck too? .050" would get me around 8cc's back using the standard chamber shape.

Cam timing is not an issue with the adjustable sprocket, it has tons of adjustment. Something ridiculous like 16-18 crankshaft degrees.
Rebuilding an OHC Pontiac 250 with EFI and a Turbo