cam ID

[sweet572]

i have a 72 sbc 400, and im rebuilding it right now and finding out everything is not exact, the block, heads, intake, cam everything im guessing has been changed at on time or another because when i check out the #s the years dont match is this normal? but my main ? is what # id's the cam here is everything on the cam

stamed on
6930X
GM42

and wrote on back side with like paint is
CV-12

anything would help thanks

[sweet572]

im trying to find out how big of a cam i can put in with out changing the pushrods or springs