I have a 1992 k1500 with 64k miles it’s a 4wheel drive and the front wheels are locked I’ve been making repairs to the frame and took the bed off a few months ago and drove it without the bed. I put the bed back on today bumper and everything and after I went to drive the truck around for the first time with a bed on. The front tires were locked and I got 20 yards to the front of my driveway. I stopped and when I tried to move again they locked back up and wouldn’t budge. After trying to unlock them in 4 wheel drive 2 wheel drive reverse forward the brake line broke. Since there shouldn’t be any pressure on the brakes I tried to back it back in to fix it tomorrow and it still wouldn’t move at all. I drove it a little before putting the bed back on in the morning and it all worked perfectly. I don’t know why it is now locked and if it is the front diff or what.

 

Sounds to me like rust might be an issue with your brakes.