5 lug swap... what width wheels?

I have a stock floored 90 mazda... im in the process of doing the 5 lug swap, and want to do a 18/20 combo. What width wheels should i be looking at for my wheels?

max of 8 up front and the rear depends on how you did it. but most likely a max of 8.5 in rear depending on offset. we need a little more info to realy be able to tell you.