Brakes Dragging Advice.
 

1969 GTO Factory power front disc car. Converted to rear (S10 Blazer) disc and hydroboost a few years ago. Great braking setup.

I recently bought some new tires and had occasion to spin the installed fronts while they were off the ground and noticed how bad something was dragging. Driver side less than half a rotation, passenger approx a full rotation. This morning I did a little investigating. I pulled the master loose from the hydroboost and verified no rod contact with the m/c. With the m/c loose the brakes still drug. The front hoses are Russell braided, 6-8 years old. They look and feel ok on the outside. With the calipers off the rotors, the rotors freely, quietly and smoothly spin on and on and on.

Calipers tired? They aren’t that old....maybe the same age as the hoses, but they did spend over a year without use while the car was at the body shop.

Is there a decent rebuilt OEM caliper available?

Probably. If you know how you might want to rebuild them.
If you put it back together and it’s still hanging up, you could always simply crack the bleeder to verify if there’s pressure hanging them up vs the calipers sticking

Brakes Dragging
 

Pirate Jacks. They sell new (not rebuilt). Off shore manufacture,, of course, but, I just bought a pair for 69 GTO. Worked out fine except, bleeder screw threads are very course and leak fluid when bleeding otherwise fine.

My son went through 3 rebuilt D52 calipers from O'Reilly's before he got a good one. Mounting surface for hose rough and leaked, no matter how tight bleeder screw was tightened still leaked fluid on another one and threads for banjo bolt bad on another one.

Exactly why I rebuild when possible, as opposed to buying new junk.

They are very easy to rebuild and have 2 parts in each kit A square cut O-ring and the dust boot. All you need is an air compressor and an hour. Place a 1x4 board in the caliper throat in place of the pads. Reduce your air pressure to around 50-75 lbs. Wrap the assembly in an old bath towel to cut the mess. Put compressed air in the brake hose port and blow the piston out, pry the dust boot out. Clean everything really well. Sand the inside of the caliper bore with some 180-280 grit paper depending on how rusty and cruddy it is in there. Remember the caliper bore IS NOT a sealing surface. So you just need to get the crap and rust out and off the bore. Surface finish is not critical. Now the piston is a different story. The piston OD is a sealing surface and if it has rust on the sides, replace it. They are available. They are flash chrome plated and it is not recommended to wire brush, wire wheel or sand them. Lube up the piston, the bore, and square seal. Install the seal in the bore and the dust boot on the piston. Use the 1x4 about 16" long to push the piston and dust boot into the caliper body. Use the board to rock the piston slightly as you push to get the piston past the square cut seal. once in, seat the dust boot carefully. You can make a home made dust boot tool out of scrap PVC pipe or you can carefully seat it with a brass drift. Seating the dust seal without the special tool can be a little tedious, but it can be done with some patience. That's all there is to it. Good luck.

I looked at every OEM replacement I could find and ended up ordering a pair of "Duralast" rebuilt calipers and pads from Autozone. Their price was the lowest, there was no shipping and their core charge was smallest. If I have an issue, there is an Autozone (none in stock and, well, I'd have to make a trip) about 5 miles from the house. My plan is to keep the current calipers and rebuild them myself for the next time.