Here are my questions....
availability .... actually found that RB5 wheels are easier to get than ZX5-SP fronts
Width is slightly different, normal 2wd tires on the 4wd rims don't work well at all ...... 4wd tires on the front of a 2wd really mess up the handling IMHO
I think there is also a difference in offset, although slight, between original ZX5 fronts and RB5 fronts ... this might make the car too wide to fit in the box (no matter if your racing at a place that doesn't scrutineer the cars running a knowingly illegal car should be punished by a public flogging ...
)