As for tires, here ya go guys, this will answer a LOT of questions if you're trying to keep your speedo somewhat working.
http://www.miata.net/garage/tirecalc.html
Rodel, your car is gorgeous. Just needs to be said. Joe, as for wanting a 4-5" lip on a 10" wide rim, you're gonna be looking anywhere from a +25 to a 0 offset. Would look gorgeous, but I think it's gonna be a good bit of work. Then again, if the result is worth the work...
http://www.miata.net/garage/tirecalc.html
Rodel, your car is gorgeous. Just needs to be said. Joe, as for wanting a 4-5" lip on a 10" wide rim, you're gonna be looking anywhere from a +25 to a 0 offset. Would look gorgeous, but I think it's gonna be a good bit of work. Then again, if the result is worth the work...