I'm COLD. NEED HEAT. GOING MAD

[Figuarus]

Guys, I'm at my wit's end.

I originally had issues with my cab heater not working. I was advised to change the thermostat in order to have more heat output from the heater core, but that resulted in my truck overheating. I've changed parts out, and have done what I can, and just can't figure out why the hell I can't get any decent amount of heat out of my truck.

I was originally running a 180 deg thermostat when I first brought it home during the spring. Eventually, I swapped it out to a 195 thermostat, and while I did get more heat out of the core, It also caused me to run too hot for my taste. eventually, my truck overheated, and I pulled that one. I went back to a 180 degree "balanced" thermostat made through Mr. Gasket. It runs cooler than the 195, but now everytime I run the fan, even on medium, the air temp coming out of the heater box is only about 10 degrees warmer than the ambient air temp.

This morning it was about 20*F...

I have replaced the blower motor, the resistor (I was having speed control issues, but it was actually the motor)and back flushed the core. I've sealed the cab as best I can, and used foil tape on the plenum to seal any air leaks. my kick panel vents have been removed and sheet metal covers with foil tape have been put in their place. All of my holes in the firewall are taped over, so I'm not getting much draft from the engine bay.

I'm almost thinking about getting a new core, but all I can find are aluminum cores. Mine is still the factory Harrison copper core.

I'm thinking about trying two things. One, I run CLR through the core, on the off chance that there is some king of flow restriction (doubtful, since I saw good flow out of the core), and two, modify the airbox to pull hot air from around my headers to heat the cab.

Thoughts?