I thought I did, but still didn't get one for some reason; I'll have to see what's messed up. (It worked before)
The hub difference sounds interesting; I don't recall any of mine having anywhere near that much of a "spacer" cast into the hub (including the SRW '65); you are saying the wheel mounting surface is 4.5" from the sheet metal brake drum center if I'm understanding you?
Here's a picture of the hubs on my truck (not a very good one, but the best I have)
http://i1067.photobucket.com/albums/u421/66Submarine/1963%20Chevrolet%20C-30%20dually/028hub.jpgI'll measure up the wheels I have when I get the chance and send you the measurements.
One thing to watch out for is the offset/width of the later wheels; I'm pretty sure they are all too wide to clear the leaf springs on one of these trucks with standard DRW hubs. The wheels I have on mine are already an extremely tight fit.
The 4.10 gears are nice; that's what both mine have in them. The no-spin should also be nice for off-pavement stuff.