84 with no heat

[ALedbetter1]

I've got a 1984 k20 with a 350. I've replaced the heater core an made sure the door closes all the way. The hoses to the core both get hot. My thermostat is a 195 and I've got the radiator blocked off with a piece of cardboard. Its a non-a/c truck so it just comes out on the floor. The air isn't even slightly warm. Even after a 200 mile road trip me and the girlfriend had to wrap up in a blanket to stay warm the whole way. Any ideas on how to get some heat flowing? My coolant overflow tank nipple broke off my radiator and i just patched the hole and did away with it. Now my antifreeze sits about 3 inches down in the radiator even after filling it full it eventually goes back to the 3 inch mark. Could this have something to do with it? Thanks in advance