I wouldn't put an 8 inch rim on a 318. It would be too skinny for me. Plus the 18x8.50 tire would be smaller in diameter as well when compared to the 23x10.50 tire. The correct size is 23x10.50x12.
darn I should of checked with you guys first.. I bought 2 ( craigslist = ag tires cheap ) thinking I might of at least been able to use it in the front..oh well thanks anyway buddy ...johnny