Thanks for all the reply's! With the above post, it lends me to believe I'd be ok with 15x8. If everything is set up right they will hook.

Took some measurements off what's in there now. 15x8 with a 4.5 backspace. Tire is a 255/75 15. Quarter panels are factory panels. I have 1.50" from qrt panel lip to the tire, 1.50" from tire to leaf spring and 2.25" from rim to lead spring. By my figures before a 10" rim with 5.5 back space would fit, but figured a slick would rub the leaf spring. Just hate to go buy slicks and they dont fit. Tried that once back in the day.