5" backspace? that's a whole bunch for an 8" rim. Are you measuring that right? Anyway, it'll fit on that wheel in the wheel house but if it truely does have 5" of backspace, you may scrub the inner wheelhouse. a 4" or 3 1/2" will clear no problem provided your springs aren't worn out. My father told me to get the "big @$$ tires" off the back of mine. I pointed out that my leaf springs are arched the wrong direction, that's why it rubs. He responded,....oh. I've been building cars for 20+ years now, and sometimes I still think he thinks I'm a dumb kid. Oh well, what are fathers for.