Normally the axle stub sticks through the flange a bit, and a c-clip keeps the stub from moving inward. With the thicker flange, the stub ends up flush so you put a washer on the end, there's a threaded hole in the end of the axle stub you can put a bolt into. I don't remember the bolt size/thread, @Tools R Us probably knows it off the top of his head, and I'm sure he's posted it somewhere as well.I guess I’ve got to disassemble everything to get an idea about what you’re describing. Where does one fit the fender washer and bolt?
Make sure the splines on your old stub aren't worn, of course. If they are, replace them with the later model ones.