You know, I had a Nova I bought after I got out of the AF in 76. Within a couple of months the heater core in the cabin started leaking. The coolant ate right through the core.....entire system was f@cked. Had to replace and flush everything, radiator, heater core, hoses, freeze plugs, etc. I wonder if what you’re talking about was the cause?
I don’t think Dexcool was introduced until 1996. ??