If you do the calc's on CR with the info: 4"bore, 11cc dish(factory 5.9),.040" in hole, .038" gask and 58cc chambers you will probably be pretty close to 9.75:1. A 10:1 piston will put you in 11:1 CR which is probably too high.
11:1 would be ok. its just a bracket car so i could get away with mixing the race gas or pulling timing and running pump gas if i wanted to cruise on the street. or i could just put the extra money into the heads...
