I just got a 1949 Plymouth a few months ago with Uniroyal white wall tires on it. I think they also say Steel belted radial. I'm trying to figure out what year or around what year they are. The width of the white wall seems to be about an inch and I think that didn't start happening until 1962? The DOT is hard to read on camera but it is:
APHF DHX 1193
APHF DHX 1193