This setup works for me at sea level, 750 proform street strip, tight converter,
[email protected] cam, 4.10 rear gear.
I have found it better to extend the idle circuit and delay main feed on my car.
IFR .035 bottom feed, .067 IAB, idle mixture 4 corner 3/4 turn area, TS restrictor .081. If I go any leaner than .081 the 60' gets hurt.
PMJ as lean as you can get without surge. I run 72s .077 diameter, PVCR .063, PV 9.5 4 hole feed, MAB .026
Cold air sealed intake air is a must and adjust idle mixture ONLY when engine is at operating temp.
A motor with no choke that cold starts and runs with no need to feather the throttle for a little bit is going to be pig rich at operating temp.
IMO an 850 at your elevation is going to be a bit much.