Your local tire guy is full of poo poo. You do not want to drive on tires that are almost 30 years old. No cracking dosen't mean a thing on tires that old. Even if garaged, tires/compound will deteriorate over time.
IIt's just not worth risking your truck on those oldies. A set of OE size tires for everyday use won't break the bank. Heck, I wouldn't even use a tire that old for a spare.
In addition, the rubber valve stems are probably shot as well.
And, if they are the original tires, over the years of sitting in Pa, hot/cold cycles have possibly built up moisture maybe causing rims to rust.
My 2009 only had 23,500 miles on it when I got it in March. Still had the original tires on it and they "looked: good. Second day I had it, it got new tires.
Just be on the safe side and get some new shoes.
Grumpaw