u/SnooDonkeys8866

I have a 1990 renix era that has been sitting for a few years with the oversized pressure bottle and I removed it and converted to an overflow bottle and radiator cap. Removed the heater valve and go right into the heater core. When trying to run it and push air out, no air comes out but I get a “gasp” sound and then nothing.
I’ve replaced the water pump, thermostat, upper rad hose, blower motor switch, blower motor relay. The blower motor is relatively new still and I checked for mice nest. The wires connected to the blower motor switch look ok and not fried. I’ve capped whatever vacuum hoses I could find.
What are some things I’m missing? What do you think?

Thanks in advance