New Huck brake cylinder castings probably haven't been manufactured in at least 50 years, so anything you get will probably be" rebuilt". Your comment about loose pistons concerns me- - - -that will also allow the seal cups to move around in the bore. When I had a choice of buying new wheel cylinders at over $100.00 each for a big GMC front brake system or doing a rehab on what was already there, I chose to do a major honing job to eliminate pitting, and make new, oversized pistons on my lathe. They worked great- - - - -good brake performance, and no leaks. Fixing brake cylinders isn't some sort of voodoo rite involving juggling flaming chipmunks while dancing naked around a bonfire at the dark of the moon- - - - -it's just a matter of making things fit properly and doing a clean job of assembly.
Jerry
