I don't have lateral-plane drawings of early (nor of late) Pontiac valve trains. I only know that setting the two rockers side-by-side it's obvious they are significantly different (needle-bearing rockers are easier to compare, since their center-of-pivot is visible). I don't recall the angle between valves and studs being different, but I'm not sure. The valves are at 20 degrees in both, but the studs may be angled a little bit differently. As for using later (longer) valves, I don't believe that would get you anywhere.
Yes, using later heads is (I think) a good move. It allows you to shop for "normal Pontiac" valvetrain stuff and a wider choice of intake manifolds- and of course many better performing heads.
Note: if you wind up wanting to tap [any] heads for rocker studs (e.g., if you bought those 7/16' bottom thread hollow studs) It's a good idea to have a machine shop do it so they are perfectly true and parallel.
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Anybody else on this planet campaign a M/T hemi Pontiac for eleven seasons?
... or has built a record breaking DOHC hemi four cylinder Pontiac?
... or has driven a couple laps of Nuerburgring with Tri-Power Pontiac power?(back in 1967)
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