Lowering and wheel question for a '67.

[laplander]

I've been browsing thru the old posts about backspacing and wheel size and am confused from a couple of posts. Does having a step side bed on my '67 make for less space then a fleetside? I thought that was one of the posts said and that made me rethink my game plan. I'm getting ready to pull my axles and have them redrilled for the 5x5 and put the rear discs on, the fronts are already done, and then go with a 4/6 drop. I was wanting to go with 17x9.5 on the back and 17x8 on the front, both with 5" bs, does that sound right? If not, how big of a rim and tire can I fit under there w/o rubbing? For you guys that have the 4/6 drop, do you have any problems bottoming out, or is it a nice compromise?
Thanks.