Been driving my 84' T/A for the last month or so after I rebuilt the little 305, let my 2001 Dodge 1500 have a breather for awhile, its got 107K on it all ready. Anyway, last weekend my wife and I were driving across town in the T/A and on the way home I notice steam comming from the A/C vents and I smelled coolant from time to time. Guess what, heater core. I've always read on these board what a PITA it is to get it out so I will tackle this job this weekend. I'll let you know how the fun went.

 

Well in the 45 minutes it's going to take you to change it. Do a search on heater core, no point in using the longer/harder procedure for newer 3rdgens on your 84.