Now it makes sense. The WK-4 has a distinctive look.
To answer your questions (my opinion):
*) If you plan to have a restored original 3/4 or 1 ton GMC, no-brainer, the WK-4 is what you need. You would need to find another rim in good condition. The odd rim you could use for a spare tire.
*) I would find a shop that has experience with the WK-4 rims. Let them look at them, appraise their condition and give their recommendations on cleaning and painting. This may help you legally (hope it never comes to that) if you plan to take the GMC out on the road. It will show "due diligence" on your part towards safety.
*) If you want an everyday driving truck, I would find modern rims, that fit you truck properly, that are made for today's tires.
