The online manual by GM and the GM heritage Center Specification book say the same thing. 1950... two fuses, one spare, mounted on "front of dash". Stop and Tail. 20A glass cartridge. (kind of a big amp sizing for tail lights)
That is the only documentation from GM I know of. Does not matter what a vendor says or if there were extra parts overlap. The correct set up is documented.
It's possible that dealers or up fitters added fuses when heaters, spotlights and radios were added....and of course PO's. If a guy, who owns a 50, buys a 5 fuse holder from a vender who advertises it as correct, from then on it's deemed correct. That's how it goes sometimes. Doesn't matter.
Any fuse box can be used on any truck. When purity is not the goal.
