Any luck finding anything? I dug a bit deeper and found that old core I knew I'd saved. Probably still have the control rod I removed also but have no idea which container/box it may be in, it's been a lot of years since I recored my heater and the rod is a lot smaller than a core.

Mike- that was the problem. The o-ring adaptor had come off inside the firewall tube. I soaked it for a couple of days and got it out. It is soldered back where it belongs now. I am going Friday to check out a couple of old heater boxes a friend has, hopefully one has the rod and (maybe) an ac evaporator. The tray on mine has a religious issue. (It is holy). I still need the heater control valve that goes to the firewall but I saw some of those on the bay. Thanks for the help and the follow up- I'll have some pics of it on here when I get a little farther along.

Hey, sounds good. I thought that would be real interesting to try assembling by soldering those two pipes together..