74 Duster Heater core swap tips

Well I tackled the heater core today, and I ran into about everything you guys mentioned in the thread. It really wasn't as bad of a job tearing everything apart as I thought. I haven't got it put back together yet, O'Reilly ordered the wrong heater core in for my car, according to the lady working behind the counter they can't even get it in. Luckily Auto zone can get it, and from the pictures it looks identical to what I have.

My cowl was definitely full of crud and what appears to be an old mouse nest. I got everything all cleaned up and ready to put back together. I'll probably finish it up on friday when I'm off work.

Again thanks for all the help, it wasn't as bad as I thought!