Overheating and power loss problem

I have an 89 B2200 with a carb and a 2.2 engine that overheats after 30 min or so of driving. I have removed all of those emission lines long ago and placed a new weber carb on recently. I have also replaced the heads, plugs, plug wires, rotor, rotor bug, water pump, thermostat, fuel filter, and set the timing yet I cannot seem to find the problems with these two situations and I feel I am at my wits end!!! I am not losing antifreeze but the truck is getting hot. What should I be looking at next?

head gasket

I replaced the head gasket last week when I put the new heads on the truck. My son and I are thinking the catalytic converter may be clogged and are planning on fixing this today to see if that fixes the problem.

Hope you get that fixed.