Nick, I think this axle identification/confirmation of what you have may take a bit to wade through to try and come to a logical conclusion. The code indicated per the GM Heritage site data shows AK333 is for a 1941 1/2ton "Light Delivery" truck axle built in Detroit on the 333rd calendar day (Nov 29th) 1941 (see 1st pic below). Because this falls into the beginning of WWII period, it is very hard to say if the axle actually got installed in a 1941 truck, or if it ended up going into a later truck as productions lines were halted to switch to war effort construction. It may seem far fetched, but an axle built and stuck in inventory during the war could have actually gotten installed in a post war 1946 or 1947 (early series) truck when production resumed. There are other possibilities, but I could spend more time than I have posting about them.
That being said, I have done more diving into several different Chevrolet Master Parts books as the descriptions of the torque tube/differential assembly are not the same depending on which book you look at. Yup, Chevrolet made mistakes sometimes. I will try and clear some of the mud from the waters in the hopes it might help ID your axle and chassis, to then figure out the truck bed mounting. For this reply, I am only focusing on the axle info. Will try to dive into chassis details another time.
Picture 2 shows Group 5.504 from the 1929-53 CMP Book. Your casting number 3657339 used for both 41-46 and 47 units. 41-46 = 55-5/8" long to carr. & 47 = 62-9/16" long to carr.
Picture 3 shows Group 5.504 from the 1929-54 CMP Book. Same casting numbers but 41-46 = 58-1/2" long to carr. & 47 = 62-1/2" long to carr.
Picture 4 shows Group 5.504 from the 1929-57 CMP Book. Same casting numbers and dimensions for year applications as the 1954 book.
Picture 5 shows Group 5.504 from the 1933-62 CMP Book. Same casting and dimensions listed for 47. Nothing listed for 41-46.
What isn't clear with the given measurements is, at what point on the tube did they measure it at??? You have measured from the differential case end to the end of the torque tube bell and your measurement comes somewhat close but doesn't match anything exactly. If you look at the exploded diagram of the torque tube where it fits into the differential (looks to be about 3-1/2" + or - deep into the differential housing), and include that length with the exposed part of the torque tube to get an overall length measurement, it may accurately reflect the 62-1/2" length noted in the parts books??? A little bit of thinking out loud here.
With all this said, perhaps some of our other Bolters more familiar with these year groups can chime in and provide more insight or details to help you? Maybe someone would measure their setup and provide that detail???
