I have a '63 with late wheels. It's a tight fit, but they seem to work just fine. My '65 (SRW) has the same brake drums, and I have drums that came off a DRW '63 that are also the same. (13" x 2-1/2") Lots of other trucks I've seen have the same wheels on them.
I'd guess your '64 has the "wrong" rear end under it if the drums won't clear 16" tubeless steel wheels. Some earlier stuff used 14" brakes IIRC; not sure how far back, though. The GM heritage center scans have 13" x 2-1/2" listed all the way back to 1960, so it would have to be the previous era or earlier. The HO72 dates all the way back to 1947 (IIRC), so someone may have done some swapping at some point.
I measured the outside diameter of the drums on both my 61 and 64 right out on the front flat area and they measure right around 13.75". I measured the Chevy dually wheels I have right now and they are a max of 13.5"(maybe a little less) inside diameter at the area they contact the brake drum. These wheels may be older style(70's-80's-90's) but no older. I am trying to find a wheel from a 2000's model to measure the inside diameter of the wheel to see if it will measure wide enough to fit over my rear drums. If someone knows this measurement I would appreciate the info. I am guessing that the late model(up to 2010) 17" dually wheels would clear but I have not ben able to find one locally but I am still looking. Anybody here have any 17's from a latemodel?
