It's something I've been putting off forever. Whenever I turn the blower on I smell antifreeze but I'm not losing a significant amount of coolant so I haven't bothered to replace the core yet. I know I should do it sooner than later but I'm wondering how different the process for an 83 is than for an 85 and up like the writeup on CoolCats.
I did it twice on an 88 tbird. make sure you buy a good core when you do it. I bought a cheap one and had to do it again the following year
I just did it in my 84. Nothing was really to different.
I'll see if I can't dig up the thread.
http://www.foxtbirdcougarforums.com/showthread.php?t=17375&highlight=heater+core (http://"http://www.foxtbirdcougarforums.com/showthread.php?t=17375&highlight=heater+core")
If you have any more questions feel free to shoot me a PM or whatever. I'd be more than happy to help.