front brakes binding

[RustyBucket]

I haven't driven either one of my trucks much for the last 8-9 months. I had some health problems and then this Coronavirus mess came along. A week ago on Saturday morning I took my '71 GMC on a driving car show with about 50 other cars & trucks. I was lightly riding the brakes along behind another vehicle cruising through a neighborhood. The brake pedal got hard, right up at the top with no travel. I was having to use more throttle to keep the truck rolling because the front brakes were dragging. I got out of the way and let it stop and it felt like I had the line lock set... and I DON'T have line lock. The front brakes were hot as hell and smelled. After it cooled off for about 45 min. the pedal eased up and it drove home normally. I took it around the neighborhood Sunday afternoon and it did it again, I had to let it cool before I could come home. Factory power disc on the front/drum rear. It's been 4 or 5 years since new hoses, pads, rear shoes, fresh fluid. Nothing was leaking so I didn't change rear wheel cylinders or frt. calipers. Probably has 4 or 5 thousand mi. since then. Brakes were fine last time I drove it a month or so ago. Guess I'll start by looking at the front calipers & see if one/both are stuck.