I think if I was setting up a set of Axial tires, first thing I would try is airsoft bb's. They will add weight, and provide support at the same time. Fill the fronts about 2/3 - 3/4 full, and probably a little less in the rears.
Can't promise it will work well or not, but with those tires, that's where I would start.
As for wheels, you should be able to find some used AX10 stock rims for pretty cheap, but you will need to glue the hexes into them to keep them from stripping.
T.
