15x7 +0 is an easy fit under 120Ys just with lipped gaurds
15x8 +0 is no real problem on the back and might be do-able on the front - I'd have to check the measurements I took off mine... I think I was factoring in the 8mm S13 disc when working out what would fit. I'll check tonight.
Do you have standard struts and brakes?
Some examples in the
wheel database threadMy current 2dr sedan has 14x6 -7 and 14x6.5 -15 (with the 15mm spacers) stock diff, struts&brakes and lipped gaurds.

Compared to that, the outer edge of 15x7 +0 will be about 9mm further in on the back and about 6mm further out on the front. They'll fit easy.
15x8 +0 outer edge would be about 4mm further out on the rear. Not a difficult fit with 195 or 205/50s. You can expect some rubbing on big bumps occassionally though. The inside clearance shouldn't be a problem unless you have really soft suspension.
On the front a 15x8 +0 will be about 19mm further out. That's not too much of an issue with some mild gaurd work and a 195/50. The question mark is about the inner edge clearance to the strut as I mentioned before...