I know it's been a while since I last really posted in here, but just wanted to say that I swapped out my heater core and so far so good. It definitely is a tedious process too and I used advice from at least 3 different how-to websites on the subject. I'm just glad its over! I took my time with it over the course of the weekend. Despite that, I still managed to snap a few vacuum lines and break my 4-way flasher switch. This is also not something I want to repeat anytime soon, so I went with an OEM core. The original was a bit of a fight to get out because I still have AC hooked up, so the box would not come all the way out. Anyway here are a couple of pics of the effort:

 

Yikes, yes I have dont his a couple of times, no fun for sure....

 

Yeah, never fun taking heater core out of a Fox with A/C!

 

I did the heater core in my 77 Cobra and my fox and it sucked on both occasions and it of course died in the winter so that was a double suck.

 

Yes, and it was quite cold when I had to replace mine too- But thankfully not as cold as it has been this week. I was just glad I accomplished the job with the AC still in there and managed to finish over the weekend. One of my regrets was that I didnt replace the bulb in the gauge cluster for my right turn signal while I had it off :-p (At least I know the bulbs on the outside of the car works)