Your stock GT-40 numbers are considerably worse from .100-.400 lift on intake. Better at .500.
Who in the hell is running .600 lift on a set of iron GT-40's? That's like an X-303 with 1.7 rockers!
An E cam with 1.6 rockers will put you at .498/.498. I'm not seeing the advantage of your numbers being better at .500 when the E cam never gets there.
If you are building a serious engine, there is no way in hell you'd pick a set of iron heads flowing under 200cfm, or 205 with a .600 lift cam/rocker combo.
The GT-40P's weren't designed to flow at .600 lift because it makes no sense to run them there. Hell, the stock HO cam .444/.444 has been getting people into the 12's for years.
People are making over 400hp N/A with the E cam and aftermarket heads. The only way your .600 lift figure should EVER come into the equation is on a stroker, or a much larger displacement engine than a 302. Putting a .600 lift combo on a 302 is stupid. All you are doing is wasting tons of engine power lifting a valve way the hell up there. Going with an increased duration cam and sacrificing idle quality is a better route for such a wild combo. You'll get better power production with it because you won't lose so many hp lifting valves.
Two different flowbench's both shouldn't be off. Based on your flow numbers (the early GT-40's seem to flow better), the P head, and the iron head are nearly the same for flow on exhuast, the GT40P flowing more intake until .500 (max lift that it should ever really see).
Based on the flowbench numbers I posted, with links to the sites, the GT-40P outflows the GT-40's everywhere. As far as the pricing on the GT-40, I haven't seen a used set for less than $400 in a good long time.
The E7TE is also a "truck" head. Guess the old truck heads are pretty decent? Maybe you can discard the GT-40P because it's a truck head, but appearently Wolfe can get stock "truck" heads to really perform, don't know why he wouldn't be able to get better stock truck heads to perform even better.
I guess jeff chambers said it best "Nearly everyone (90% or more) running competitively in T/S has switched to the P head because it just flat-out makes more power."
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