This is a popular topic. Searching around will reveal a lot of discussion worth reading.
Be sure not to confuse offset with backspacing. They both measure to the wheel mounting surface, but from different perspectives. Backspacing is measured from the inner wheel rim and offset, can be + or - , is measured from the wheel centerline.
Reduced backspacing is generally required for tires over about 10.5 inches wide, to keep from hitting when turning the front wheels. 8" rims with reduced backspacing are available. A lift is needed to clear tires over about 28" in diameter. Largest tire that will fit a stock Samurai is 215/75R15. Useful wheel info at:
http://www.rsracing.com/tech-wheel.html