i have 17x8's all around with 245/45/17's in the front they a 8" wide tire which are perfect and in the rear i have 275/40/17's which are a 10" wide tire which i love the wide look, the difference in look is in the front the sidewall is rounded while the rear is slanted but lookin from behind the 275's look awesome

you should have no problem puttin a 245/45/17 on your rims, but im almost positive the rims you have are 17x8 and not 17x7 unless there not a ford, cobra, steeda, or saleen rim because all 17's made specifically for the stang are 17x8 and some are 17x9 i havent seen any 17x7's.

 i worked for town fair tire and have seen and worked on many stangs and have a indepth knowledge of stangs

please get back to me and let me know what kind of rims they are because if they really are 17x7's ill get you the proper size for you

Well I have 205/40/17 on my stang n am sending u this pic so u can see 'em n make ur own desicion