You can fit 245/60/r15's under the rear for sure on a 15x8 rim with 4.5 inch backspace, I have 255's on mine with those same wheels n measurements n they are ssuuuuper close.... I think I am gonna hafta roll the fender lips up for a bit more space....
I have 215/65/r15's on the front on 15x7's.... theyre way good on space...
I have heard someone on this sight say they have 15x7's all the way around and 225/60/15's all the way around n they are super happy with them...
So, since you don't have a ton of Horse Power on those wheels, I'd go 225 or 245/60/15's in back
and 215 or or 225/60's or 65's /15's in front
I used Cooper Cobra Radial Gt's tires on mine cuz they are rated 123 miles per hour constant speed and they are super inexpensive! I got mine from discountiredirect on ebay for waaaaay cheaper than anywhere else even... I paid 390 bucks no tax no shipping, for all 4 tires...
N I used these wheels from wheel vintiques, but I bought them from Summit for way cheaper n no shipping....