Enough Tire

Yeah, I was afraid of that. Right now I can't find any rims that are 4.5 inch backspacing for a 5 on 4 SBP. I was wanting to go with a 10 inch rim and 275 60 R15 as suggested by AdamR, however I can't find anything close. Will a 275/60 R15 fit o.k. on an 8.5 inch rim?