One thing you guys have missed is the altitude. DA of 4500 feet cuts power by maybe 15%.
Tucson is altitude 2600 feet, plus a hot day???

A few years ago I ventured to Phoenix in the summer, truck was jetted for 5000 ft. I was expecting lean surging, etc. But it ran normally. The only reason I can think of is the air was not dense because of the temperature.

I prescribe compression and if possible a better combustion chamber. I also think the cam is too big, kills bottom end, and the heads are too small, kills the top end.

But what do I know? Try advancing the cam first, see if you can get a better 60'.

R.