ClassicCar

Park - I believe you're right. The stepdown rearends are quite a bit narrower that the pre-stepdown rears, not really a great 'swap' candidate.

HudsHornet - You do what you want (what makes you happy) with that truck. The 'Twin-H' is a nice option, and can be made to fit into the truck without too much additional effort, as can the 232 and 262, and 308 (I mention the 'Twin-H' separately, as that addition to the engine was used for both the 262 and the 308 engines, and technically should even fit a 232 engine). The 254 eight is also another option, not seen as often as the 'Twin H'.

According to all the literature I've come across, no Hudson pickup ever came out of production with an 8 in it. They came with the 212 cu in splasher or some 175 cu in, for the late 30's & early 40's basic, lower end commercial vehicles. 'Big Boy' models and later trucks all came with 212 cu in, and the larger 212 cu in was possibly (?) an option on the commercial series that came standard with the 175 cu in engine.

And, Hudson trucks also didn't come from the factory with labeling on the sides of the hood. They had rivets that filled the holes - See the picture below of this, from the last National -

All-in-all:
Just because it is there, it doesn't necessarily mean that they came that way from the factory -
- An engine goes bad, it is replaced with what is around, on-hand, or easily/cheaply obtained, etc.. Or, wanting more power that the 6 cyl splasher (212 cu in, or in some cases 175 cu in), an 8 was put in, upgraded to a 232, 262, 308 or 'Twin-H';
- Most likely dealers put the badging on the trucks, or the subsequent owners decided they wanted the badging on them. That, or possibly the hood was replaced with one off of a car and the badging kept as it was (better than holes in the hood).

And -
Both of the '46 trucks I currently own have the badging on them - put there at some point, and both have the 'fender spears'. One also has the car fender mouldings, wrap-around bumpers and a Commodore steering wheel too, most likely installed as an after-market option(s)...

The eight or 'bigger six' (232, 262, 308 and very popular 'Twin-H') are very popular swaps for many Hudsons, be it pre-stepdown or even stepdowns... As has been said many times - these are old trucks, and in a lot of cases have changed hands many times. Hard to say what they've gone through or the changes, modifications, or adaptations that have been made to them over the years...