Carb tuning help

[Classycustom71,95]

Hey guys,
i got my rebuilt 350 with mild cam into my truck last weekend and now am having some troubles getting the carb tuned right. its a 1806 - 650cfm edelbrock.
I am in Calgary where the elevation is 3438 ft, I have changed the rods to the .065 x .042 rod. and that has helped it run a bit better but i will still get a backfire after getting it to about 3500 rpm and letting off the throttle, it still hesitates alot at anything less than a 3000 rpm gear change.

i could keep trying different jets and rods but am unclear if i should be going richer or leaner?

my timing is also currently at 6 degrees.