I'm shopping too
I'm doing a 5 lug conversion, and hope to run 7s and 8s.
Fit is also dependent on offset... early offset (23mm) wheels will need less spacer, if any, than late.
If you plan on aggressive driving, or racing, you also need to watch the scrub angle on the fronts... bad scrub angle will make your fronts fight each other and you lose grip. I haven't done the calculations on that one yet, but I'm sure that 7s can be setup properly, not sure about 8s.
Tire size... overall diameter will affect your effective gear ratio. Width is dependent on wheel width and clearance.
How you plan on driving the car will make a difference in your selection.