What cam should I get?

bobscuda67 said
My 273 had between 135 to 144 lbs. with the warm cranking check. I measured everything and it worked out to be a 8.5 to 1 motor. If yours is stock low comp. its around 8.0 to 1. Bob

If I do the readings on each cylinder then what math do I do to work out what compression ratio I have. This next question is how do I find out what gear ratio I have without going in the rear end? I know that I can put a strip of tape on the drive shaft and count how many revolutions it turns as I turn the wheel one revolution but I don't know if that would be right.