Old faithful lives!!!. Brother, professional mechanic back in the day, was here. Truck fired up with turn of key, Bit of revving and inspection and he found the leak. As I suspected it was a leak under pressure only. There is some kind of small gizmo at the top, front, right on engine that has something to do with the heating/air conditioner with a two hoses (in/'out) attached. coolant leaks when radiator pressure comes up. Brother says to just connecdt the two hoses together and cut the gizmo out of the circuit. I won't have A/C but that died 20 years ago anyhow.
Off to town with it in the morning to body shop to have right rear taillight lens installed (backed into a tree) then to the grange for an appointment to work on the hoses.
Shucky darn, I was all set up to go buy another PU tomorrow.