More info always helps.
What is the engine going into?
What is the application? (daily driver, street, performance, race?)
What transmission, stall speed, rear gearing, tire size?
What are your performance expectations?
What are your budget expectations?

Also, you don't have to pull the heads. You could turn the engine on the engine stand to where the spark plug is the highest point. set the piston to TDC (both valves closed or remover rocker arms), and cc the chamber volume directly by filling through the spark plug hole.

Assuming a 0.030" over bore (4.350" bore x 3.75" stroke) the piston swept volume should be 55.73 cid = 913.44 cc's.
Here is a list of chamber volumes above the piston at TDC and what the compression ratio would be:
CC's CR
90 11.16
95 10.62
100 10.13
105 9.70
110 9.30
115 8.94
120 8.61
125 8.31
130 8.03

You would want to cc the chamber using some oil so it won't run past the ring gaps, or cause rust in the chamber/bore.