Thanks for the picture. The difference in the '70 isn't the hub; that's all part of the brake drum, which is certainly much different than the earlier ones I have.
I'm not sure why the rear hubs on your DRW trucks look like my SRW hubs; maybe something weird GM did? I'd say it was a year-model thing, but if your '61 looks the same that doesn't make sense. Maybe someone swapped them with another junkyard assembly when the brake drums needed to be replaced later on?
I don't have them apart to look at now, but IIRC my SRW had the WMS cast further out like that; presumably to change the WMS-WMS width and keep the load distributed as intended over the inner/outer bearings, but using all the same parts otherwise (or that's what I thought/theorized). Maybe someone swapped them for more tire clearance, in that case? Hard to say, I guess.
I'm interested to hear if the 28177's work. Scrape all the dirt off the edge of the drums and snug them up good with a couple lug nuts when you check; it's a VERY tight fit, and if it's not flat/tight to the mounting surface or it's caked in grime it'll touch. It's even less than an 1/8" gap; actually probably more like a 1/16" of a gap when bolted down and looking through the hand holes. Tight!
I knew that whole part was the drum but was unsure how to explain the differences in "step out" from the actual brake part of the drum.
I do not have the wheels off the 61 but I am going to take them off and recheck the rear drums as I think they are the same but now you have me second guessing my memory. I never measured or took pics of them and the 18's are still on it.
I tried several different dually wheels so I may have already tried the 177's but I was not looking at the part #'s at that time. I know I measured them and they were the same as all the other dually wheels other than the 2007 dated wheel so I am sure I tried them but I am still going to check. All the wheels, other than 07 wheel, I tried hit the drum very solid before the studs even got close to the holes. The 2007 wheel hit and the studs had just started but did not come through. I will get this figured out.
