I have a six lug 1/2 ton 1946 GMC and I put CPP disk brakes on it. I currently have Wheelsmith 15 inch artillery wheels and there are no clearance issues when using the narrow wheel spacers that come with the kit. I could make the stock 16 inch wheels fit if I grind about 1/8 inch of metal off a very small area where the wheel center rivets to the rim, again, not a lot of material but just the little tips of metal that appears as excess. I think it wouldn't effect the structural integrity of the rim because that 1/8 inch is just the very tip of the webbing and not anywhere where the outer ring and inner part of the wheel connect. I temporarily added 1/16 inch washers between the wheel spacers and the rims and the 16 inch wheels didn't rub the CPP disk brake calipers. Because I plan on using a 16 inch for a spare, I'll grind off that metal tomorrow and send a link to a picture of what I am talking about.
