Ford aluminum intake manifold with Eldabrock 4 Barrel Carb w/riser undercarb to clear valve covers.
Since install radiator blows out anitfreeze when ran.
Took thermosat out still have same problem.
Air pressure builds up in the hoses but still blows in overflow tank.
Radiator is brand new.
When the original carb and intake manifold was on had no problems with antifreeze.
Could it be the intake manifold?
Bad water pump?
Or could it be a cracked head gasket?

i would pull the intake back off and begin checking it against the old one. make sure a water jacket isnt getting exhaust from a gaskek. is that all you changed ? just the intake? or did you do some head work as well? why did you swap the intakes? if that is the last thing that you did before the problem arose then it has to be the problem or the main part of it/

I'm not sure how you'd get pressure from the intake into the cooling system, but it sure sounds like that's what's happening. Or installing the intake somehow disturbed a head gasket and now that's leaking into the cooling system. You can have a radiator shop test for hydrocarbons in the cooling system. If they're there, it's a head gasket or cracked head.