Yes - you do have to be true to Earl and to the early 50's BUT - remember that motorama cars had stuff never seen anywhere before - that was the purpose of the motorama! So - something that would be unobtainium in 1952 is still something that maybe shoulda/coulda/woulda been on a vehicle in a motorama in 1952.
If a (suppose) '55 Packard tail light looks right on your truck - do it!
maybe narrow vertical light running up the rear-most stake pocket might be something that GM would have done way back when to stir up interest in the pickups.
You are already chopping & sectioning to make it look more modern, more sleek. You will already be making some changes to the schnozz, so why not do something a bit more "futuristic" to the hindquarters? You do not need to just pirate lights from stock vehicles that existed then - the tails of the other cars in the 1952 motorama mostly featured lights that never appeared anywhere at any time - so why would GM have been so constrained if the cab was chopped & sectioned?
(Just thinking ....)