you would have to cut a BUNCH off of the head in order to bring the 7.9:1 CR up to the 10.5:1 of the 1970 heads. and that would also require cutting the intake.
as you reduced the height of the head, you lower the attachment point of the intake and necessitate narrowing the width of it and sometimes also slotting the bolt holes.
and remember, there's a big dish in the 75-76 pistons. it doesn't matter how much you cut the head, you're never going to get that dish area back without a new set of pistons.
it would be better to just shell out for a set of aluminum Stg 1s from TA. they flow more out of the box than a max effort porting job and alum can tolerate higher CR.
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