Hy Snellen, pits are common in the center of the wheel cylinder and cause no problems as the cups (seals) do not travel over that area, pits toward the outside of the cylinder bore will cause the cups to wear and leak prematurely. You can hone the cylinders out, but not so much that the cups will go into the bore without folding in the lip of the cup, if you hone so far that your pistons are a sloppy fit in the bore you should have a machine shop make you up some new ones which are a tighter fit. Brakes are the most important system on any vehicle, not just for you but for those traveling the roads with you, so don't skimp on their repair. RockAuto lists Raybestos wheel cylinders for the rear of your truck under p/n WC14499 $63.79 and p/n WC14500 $74.79. Hope that helps.
