challengers do come in 4 stud.
you will NEED flares.
your car will need too be lowered quite alot or itll look shit, and neg camber. (mexican)
depending on how much you lower it, your guards will need to be cut for more inner clearance. (scrubbing)
tire size also effects whether itll scrub your guards. profile too high youll scrub. width too crazy youll scrub. profile too low looks gay. width/stretch too much looks/handles gay.
having said that id take fat tyres over skinny stretched tyres anyday of the week. however i couldnt find any wide tyres when i was looking. so i got 205/60/15 for my 9.5" rims.
finding decent width 15" tyres is very hard. youll never find off the shelf.
when car is lowered, itll neg camber naturally. youll need adjustable sussy bits so you can tinker it. (too much handle shit)
- also affects whether itll scrub.
i suggest you learn and research about wheel widths/offsets and which is needed for the z.
ps. are you sure ccws are only 2500$ new?
i paid more than that for my old old old 2nd hand hayashi streets and ssr meshies.