[PAUL K]

Originally Posted by 4birds

Anthony, which heads do you have? If you have 71 HO heads, you must use a 69-71 intake crossover. If you have 72 7F6 heads, you must use the 72 intake crossover, as it is different.)

You are correct when using GM parts, however most reproduction crossovers were designed to work with either head.

[bird72]

Just to clarify 71 heads and intake is what we have. I have oversize RA Ent new manifolds. In my prior aborted HO attempt the cracked factory manifold nightmare ensued and this time decided for once repro was a functionally better route. I need a crossover, have offer on repro, so doing detective work on opinion / fit / quality, it looks nice in pic. Slight appearance differences probably would not matter to me. Of course a 71 GM one would be preferred.

I looked on ebay on 71 head pics see some have all holes (?) wondering if some 197 came double drilled and some not. Or are double ones owner modded.... I lean towards drilling head as smart, but if it is of no value and degrades head I guess I would not, but really don't care in this area also as to head "virginity" too much unless drilling is just dumb move stuff value wise. But it does seem smart engineering wise to drill for grins.