[EricH]

I'll answer a later question first: You should be able to swap with any other wheels, GIVEN that they are the same size or that you correct the gearing (if needed). So, if your chassis has 6" wheels, and you have a different set of 6" wheels with the same attachment system ready to go, it's as simple as swapping wheels. If you want to change wheel size, you'll have to account for that in the gearing.

The Hi-Grip wheels that you're talking about will probably be OK for the running track. (Might be too grippy, but that's not too hard to fix.) You should be able to swap for am-2648s with no issues for indoor (gym floor) use. Street/sidewalk, go with a used set of whichever you want to go with.

If you're really tricky about it... you build up a spare set of wheels, complete with sprockets, for the "alternate surface", and have them ready with the robot, so that a swap will take about 10 minutes for all the wheels (OK, so maybe I'm exaggerating... or maybe not!).