Holleys have always been problematic for me, mostly due to stuck floats/needles resulting in severe flooding.
IMHO, it is hard to beat the Quadrajet. At your altitude, you may have to re-jet no matter which carb you go with.
I have a nice 600 cfm vac secondary Holley if you are interested. The 350 runs great with it, but it was removed because......it had a stuck float.
418 miles on 19 gallons of gas. Can't beat the BBD !