That carb has vac secondarys. Adjusting the float is not hard, a little low to start would be better than high, once it's idleling fine you can readjust the float.
I'd start with idle screws turned out 1 1/2 turns, that should let it run at least.
Why it wants to race kinda says it's getting gas from somewhere until it uses it up and shuts down.
I think I'd pull it off and re check what I did to make sure things are the way they are supposed to be. At least a holley is simple to tear down.
Dan
