tire size? up or down

I picked up some tires today from a buddy, I got a pair of 215 60 15s and they are to big for the weld racing rim, I think I have the 4 inch rim so they will not fit. I also got some 275 60 15 to try on the rear but I think they will be a bit to close to the rear leafs.
So I will go with 245 or 255 for the rear but what would be good for a 4 inch rim? 195s?
Thank
AL