old nut,
just wanted to clarify that the rim size for your 1949 3600 was actually 15" and not 17". my 50 has 17's with the lock ring and they are (as brendanm stated) much "safer" to work with than the split rim jobbies.
as far as radial vs. bias ply. i've run bias on mine since i've owned the truck and my grandfather ran bias since he bought it new. they do wear faster and handle like a bad shopping cart on some road surfaces, but they do keep it original.
i've ordered tires from coker a couple of times. the only thing i will say is that the firestones and the tornell's have worked for me up until the last set i ordered for the front. i wanted to get back to the original look of the truck with the bigger tires (firestones always looked a little small) and the tornell's shook like crazy on the front. ended up with the bf goodrich's and they have worked out well. a little pricier, but worth it so far. seem to be wearing pretty well too.
you should be able to get tubes from coker as well.
