The only difference in endbells from yok, top, or epic based to where you'd need a different endbell is for the big comm motors. The brush hoods on the V2 endbell are super close to the comm, so if you pyt v2 endbell for a small comm motor on big comm motor the hoods will more than likely hit the comm if it fits on at all. Other than that I don't see any other difference between brands. On "normal" endbell mod motors you can put any endbell on any motor, just have to switch hoods out to stick with the stand up or laydown setup you're replacing.
The V2 endbell you bought is for stock motors. That's why it has bushings, not bearings. And I don't think the endbell will even go onto the Reedy Quad because of the big comm. It won't physicaly fit I don't think because of the brush hoods. And the reson for soldering directly to the brush hoods is for maximum power to get to the brushes. The original protypes for the V2 endbells didn't even have soldered power wires. They were held into a hold with a set screw if I remember right.