Anyone know what month GM cast numbers went from 3973487 to 487 "X"? I know it's around 1971 and 1972. My NCRS book says "later 1972" cars had 487X heads, and before I shell out the bucks I need to be sure.
Also, is NCRS judging casting numbers and dates for heads (you can see the driver's side casting # with oil cap off), or is it just the casting symbol on the front?
Thanks, Chris (NCRS 36056)
Also, is NCRS judging casting numbers and dates for heads (you can see the driver's side casting # with oil cap off), or is it just the casting symbol on the front?
Thanks, Chris (NCRS 36056)
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