15x8 is a bit big up front. Even a 245 is going to rub up front on an '89 unless you take a softball bat or something to your wheelwells.235's fit fine on stock 15x7s
Out back, 15x9 by itself is probably ok, but it really depends on the tire. Should you go with a 275 you are going to have problems as well, remediable probably by removing (or flipping) the quad shock, and a little fender massaging again.
If you're just after the 'look' run 235's up front, and maybe 255's out back. Otherwise, going around corners your suspension/tires are going to rub on you and it might not be worth it to ya.
I dunno, just my opinion.
FWIW, 15x8 (or 15x8.5) rims fit 10" rear drag slicks GREAT!
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1984 Ford Tempo AOD--- RIP