Thanks all! I think I'm learning stuff...again. Ouch.
Just for fun last evening while fixing a flat on my son's bike I tried his 700 rear wheel on the 520. His is a recent Jamis with el-cheapo Shimano components. Jamis website lists the wheelset as " Alex AKX R1.0 wheelset 700c 28H radial front/ 32H 3X". The derailleur was able to shift to 7 of the 8 without any adjustment, no interference. It just wouldn't quite get to the big sprocket. It looks like there is plenty of adjustment left in the limit settings and there appears to be room left to set the brake pads on the wheels. It fit the frame with no spreading, no need to force anything at all. It really seems like it works?!?!? Am I missing something or should I just swap out wheels/tires, adjust it and see if I like it?

Thanks again!
JT