If I understand you correctly, you're in part confirming that you can run an aftermarket high elevation head, PAR 13.6:1, down low. Yes, it's doable, but not on pure pump gas. You must run a higher octane mix - pump + race/av, etc., to avoid deto at low elevation. I believe Brad could give you a pretty good guideline on how much per the elevation change.
I think you also asked if a stock does it, can an aftermarket do it - stock pro compression is 12.5:1, which is safe down to sea level. Yes, aftermarket low comp (12.5:1, e.g.) heads can be run down low. You're still just giving up hp, 5-10, running that at 8000 feet. If you ran a 12.5:1 against a 13.6:1 head to head at 8000 feet, you would notice a very significant difference. You could run heavier clutch weights with the bumped up compression at higher elevation also, of course. Lower comp aftermarket heads from PAR, RKT, work the exact same way as stock. I do know the RKT 12.5:1 heads will run straight 91 pump at 1000 feet with no deto - seen it personally, FWIW. Haven't seen the PAR low comp head in action down low, but clearly sledneck_03 has.
Taking a 13.6:1 from 8000 down to 1000ft will need alot of race, e.g., not just a gal or two. Boost, alla Torco, won't come close, either. FWIW. A 13.1:1 would also require a couple gals of race just to be safe for WFO pulls down low. Just trying to help. JMPE (I do run high comp heads on a pro, and have also done it with doos over the years. Familar with the drill, swapping domes, running race fuel mix, etc.) Swapping domes on a pro is pretty easy, just in case that's an option for a week or two out west, also. Good luck.
