David,
What is the chrome and stainless that you are referring to? Many of those items were most likely factory installed. I think that chrome front and rear bumpers were factory installed on 3100 trucks in 1951 (they were in 1950; someone with a Truck Data Book can correct/confirm this for 1951). Spotlights and a chrome grill might have been installed by a dealer on a non-Deluxe (3 window) truck in 1951, but if a dealer was ordering the Deluxe Cab & Equipment option (RPO 390: chrome grill, rear corner windows, bright (stainless) window trim, etc), this would have been installed at the factory.
I have had two Deluxe pickups and neither had the bed wood painted body color. (Not related to your question - do you have a 9 board bed or an 8-board bed?)
If you do not mind me asking, why would the original dealer paint the bed wood? I can easily understand why the bed would be painted body color during a repaint.
Do you have a 1951 Truck Data Book? Do you have the 1951 Restoration Packet from GM? These might help answer your question. Let us know what you find out
Tim