In those years, Chrysler did what they called "running changes". Whenever they made a mechanical improvement, it was installed when the parts were available, and didn't wait until a model year change to upgrade most things. What that means is that if they made improvements in the brakes, the "new improved" brakes had to fit onto what was already existing. That means that if there was an improvement, the new stuff should be able to be swapped as a complete system. A brake improvement would likely have involved the backing plate, the shoes, springs, wheel cylinders, and maybe even the drums, but it probably fit on the original spindles. Major changes, like spindle changes, or axle changes coupled with brake changes would have been done at a model year change, or a major body redesign.

That said, Dodge dis a major body redesign between the 47 and the 48 model years, and another major body redesign between the 53 and the 54 model year, and another between early 55 and late 55.

Personally, I'd bet on the same spindles between 39 + 53, but the shoes, springs, wheel cylinders, and backing plates might be a different story.

Might find the guys at www.robertsmotorparts.com helpful, they know a lot about these trucks, and have some brake parts available. Gene