IMHO 16 is too big for a sprinter, however Jon's (raceflo) car has 17s on it at the moment I think (you can see pics on his website) and the car looks nice =), but I think for that sort of car (ie uber powered) tyre diameter is far more important than a bit of reduction in wheel size for rotating weight reduction
I believe that R33 hubs are 5 stud and s13 wheels are 4 stud...
Maybe you should think about running s13 coilovers if this is what you really want to do, then the s13 wheels will fit![]()
You will also get some quite adequate brakes...