Yes, right on and thank you! It’s a little hasty to say grinds A/B/or C at this point. Even though the 74 cc chambers help, if it has some old school speed pro pistons that are set .080 below deck combined with a .050 head gasket (for example, hopefully it’s nowhere close to these figures) all these choices may be too large.
Knowing the the cranking compression is key here! Being we have a cam card, knowing the installed ICL would be a bonus for calculating the actual compression, to within a couple of percent anyway.