Rally wheel backsaping and going to 17's

[smashingchuck]

OK, so I've got the 17's that used to be on my 78 just laying around. Meanwhile, the skins on my DD are getting tired, plus I bent one of the wheels the other day in the snow. So, my thinking is that I need a wheel, and 4 new tires. As long as I'm buying tires, why not get tires and throw on the 17's?!! Easy decision, right?

OK, so here is the deal. My 17s have 4.5" backspacing and are 8" wide. Right now I'm running the factory rallies that came on it in '91, which i presuming are 8" wide. What would the factory back spacing on these be? I hoping they are the same, as I have no need to tuck the tires in anymore.

Also, what size / brand tire should I be looking at. I would like quality M+S tire, as I drive this truck year round here in Michigan, back and forth to work 50 miles a day, down dirt roads, two tracks, and in the snow and ice. I currently have 235/75/15 Nokian Vativa's which have suited me very well. They were brand new when I bought the truck and I was skeptical of them, but they have turned out to be a pretty decent tire. I would like to go slightly taller tires on the 17's.

thanks for the help!
chuck