wheel/ tire decision

on a 17x8 rim with 4 /12" backspace you should be able to fit 245/40r17 in the rear. 245/45 might be a little close

in the front you should be able to run 235/45r17 i think. i know 245/40r17 there tends to be some rubbing issues

p.s. if you are having trouble visualizing how the tires will look in comparison to each other or to stock tires, check this place out:

http://www.rims-n-tires.com/rt_specs.jsp?postId=906


i found it invaluable in figuring out what i could fit on my car.

one thing though - not all tire sizes/combinations are actually manufactured, so make sure you can find a make/model that makes both sizes before you go to your local tire shop

I'd suggest a little more back space, otherwise you'll be needing to roll the rear fenders. Check out Dodgestang's tire/wheel chart.
I'm running 17x8's with 4.75" b.s. and 235's all around. Rear end isn't stock width. Front end is. Pictures on on web page in signature. These are 17x8 4.75" back space.
With the 4.75" back space on a stock width rear end and a quality Panhard bar, or Watt's link, a 10" section width tire (like a 255/45) would tuck in a rolled rear fender on a well built car. Some cars aren't built so well, so a 245/45 is a safe bet with that backspace on the rear. 225/45 is safe bet on the front with a 4.75" back space. 235/45 on a well built car fits really nice w/o rolling the front fenders, and just a little negative camber.
The above information is based on a car that will be driven through corners agressively. For the straight line drivers, and street crowd, you can go bigger
Good luck,

Wheels

Hi

There was an article on this in the September issue of Mustang Monthly.

It suggested the following:

17 x 7 3 3/4 to 4" Back Spacing 235/45-17 tires 9.4" Tread size 25.46" Height
245/45-17 9.8" Tread size 25.82" Height

17 x 8" 4 3/4 to 5" B/S 235/45-17 tires 9.4" Tread size 25.46' Height


Cheers

I can't remember the total backspacing with spacers and all, and on a '68 like I had vs. a '66 this may not even apply, but I ran 245/45ZR17's all the way around with no trouble aside from some minor wheel well rubbing on HARD (suspension-bottoming) bumps up front. This was on '03 Mach 1 Magnum Heritage rims.

I'm running 17x8-4.75bs w/235-45-17 on all four corners. (shelby drop) 620 coils 1/2 ring cutout, 4 1/2 mid eye leafs (need to drop the rear another 1/2")
just make sure that you re-align your front end to the correct (more aggressive)specs (can't remember them but someone will chime in).
Don't think I could of fit 235's with 4.5bs.