I'll also post my experiences. I wanted 9.5" wheels. The least amount of backspace I could get in a 9.5" wheel from Centerline was 5" (factory is 4"). My 17x9.5" 5" backspace Centerline wheels will not fit on the back of my car without one 3/8 spacer. This gives the necessary clearance for the calipers. One 3/8 spacer was also used on the front to clear the tie rods, but after further investigation I found that when we mounted my wheels on a completely stock 80 Corvette we didn't need the spacers up front. Infact, we had no choice. The stock studs were too short for use with a spacer. The only thing modified on my rear suspension was the replacing of the park brake cable to the top of the trailing arm, which again, we found out we didn't have to do. The retaining clip that holds the cable in place just barley rubbed the wheels when they were mounted on the 80. We rotated the clip to a different location and proceded to drive the car for three days without problems. The only thing that scared me was the fact that we barley had enough stud grab on the lug nuts due to the shortness. This will cause alot of flex and i'd highly reccommend not doing this when the car will be driven in abusive applications. Before I got my 74 it allready had extended length studs.

The other thing that bothered me when the wheels were on my car was the fact that they inside of the wheel/tire came very close to the end of my 360lb monospring. I won't lie, I actually did some damage to the wheel (where it can't be seen) because of this. The only fix was to add another 3/8 spacer and tweak a little bit of negetive camber into the back. I totally didn't want the negetive camber with the way my IRS is setup but I had no choice. By now your probably thinking i'm crazy for running two seperate 3/8 spacers on the back, but I left on a two week holiday to the U.S. where I went to the drags, autocrossed, and drove 900 miles either way. I never once checked the torque on the wheels until I got back home. They were as tight as when I left. I'm not sure where the myth/rumor came from with regards to spacers. Maybe i'm just lucky, but I was never once worried about that. If my car wasn't so low in the back I would have never had this problem. The 10" adjustment bolts are what caused the problem. They brought the ends of the spring too close to the tire/wheel. If I had stayed with a 7" or 8" bolt the ends would have been riding inside of the wheel.

On my 74, the 17"x9.5" 5" backspace wheels with 245-45-17 (and all spacers installed) tires netted a perfect fit. They don't stick out in the back or the front and only rub the sway bar in the front in situations where you have to make full tilt u-turns and the like. This was done with completely stock trailing arms (other than the park brake thing) in the rear and there is still some clearance to be had. Enough that I feel confident about mounting 275 tires on the back. As Gkull said before, the frame is the real limiting factor in the back.

Now the only thing I can do about the two 3/8 spacers in the back (and the - camber) is to get Vette Brakes to make me a custom shorter spring. My measurements tell me that if they take 1.5"-2" out of the center I will have all the clearance I will ever need. The issue this brings up is that the springs end bolts will have to have a new location slot on either trailing arms so they will line up straight with the corresponding holes in the spring. I'm still thinking about this one, as Toms Differential's hompage lists some offset trailing arms, but they also say it requires a shorter spring. I'm going to get busy on this idea...