Not to burst your bubble, I have worked on this series of truck since they were new, actually well before then. Get the wheels off, if the lining is more than 1/2 gone, replace and buy drums same time, cheap investment especially if going to be relying on them. Wheel cylinders, throw the old ones away, if you want go ahead and hone one or two, if there is pitting of any volume inside the bore or if the anodized coating on the pistons is corroded and flaking, throw them away!! Again, cheap at half the cost if you wreck the truck or they constantly leak.
When you bleed them after the work, bleed at the master first, then the Hyvac, then the closest stepping out to each until to the furthest wheel from the booster, that will flush it pretty clear.
The caution on the lining and drums is as this, shoes less than 50% will only last a short time and you will be back into the wheels, new lining /old drums, don't mate up surface to surface for a long time limiting stopping power, glazed drums are the pits for not holding. Old drums turned, look at the inside of turned old drums, you will see hard spots and high domes all over, that is where the steel has work hardened and does not bode well for new linings. New drums/new linings, take it out after you know the adjustment is good and no leaks with a full pedal, take it onto a high speed low travel road and get it up to speed, do a few panic stops up to the point of locking tires, get the brakes seated and hot, let it cools then re-adjust, will hold that adjustment a long, long, long time.
PS, fix the parking brake, they are not that expensive, the block under the tire looks cheesy and works about as well.