Holley 350 rich as can be.

Main jets have a bit to with idle; they feed the fuel into the bottom of the idle wells and the air bleeds feed in at the top of the idle wells; so a change in main jet may require a change in the idle mixture screws. But the final idle richness is set by the mixture screws regardless of main jet size; you don't change main jets to change idle richness.

1066' above sea level is not much altitude.