Thanks for the info, was thinking P255/50 R17 and P275/50 R17, therfore they would fit.
I like the Michelin Pilot 3's but they may not come in 17's.

The back-spacing or offset is key to fitting big tires.
From my measurements, zero offset works best with A-bodies.
Note: wheel width is the bead width plus one inch, so zero offset on 8" wheels would have a back-spacing of (8+1)/2 = 4.5 inches. 9 inch wheels with zero offset would have 5 inch BS.
Most 8" OEM wheels have only a 3.5 inch BS. Again, from my experience, 275's on 8 inch OEM rims are very tight at the fender lip. If you have replaced rear quarters or the axle is not perfectly centered, you're likely to have some rubbing on hard bumps or turns.
The '68 - '72 style A-bodies tend to have a little more room so the 275's tend to be an easier fit.

If the rear end has been replaced with a pre '68 rear (one inch narrower), then 8" OEM rims should be pretty much centered in the wheel well.

Lots of variables on old cars, so to be sure, test fit or measure.

There are guys running 315's on the rear (on '68-'72's) with no rubbing and (reportedly) no modification. The BS has to be near perfect to make that work though. And if you're running 15x10's, zero offset (5.5" BS) can cause rubbing on the lower shock mount - often dealt with by grinding a little off the shock mount. 16" and larger wheels are usually OK.

Your 275's should be fine, but without knowing the BS of your wheels and/or any other modifications to the car, no one can say for sure.

Thanks for all the info.......... that's exactly  the general issue ie., Backspacing. The car is stock original rear end with 

upgraded upper and lower control arms, springs and adjustable shocks, so yes measuring will be needed.

 

L

bzbaz63 wrote:

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My tires rub a little on the right side only if I lay the rear suspension down 2 to 2 1/2 inches more which I want to go to 1 1/2 later after I drop the front 2 inches more.
What can I do to center the rear to the left about 1/4 - 1/2" ?

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 I'm not aware of any adjustments to centre the rear end, or move it left/right.  Maybe someone else knows a trick (short of a frame machine)?

Is it possible the differential is centred in the frame and your one quarter panel is off?  Can you get a measurement from the frame to the wheel well lip on both sides?  Same from the frame to the outside of the brake drum?

For 1/4 to 1/2 inch, rolling or trimming the lip of wheel well might solve the rub.  A baseball bat can work well for rolling the lip.  Start with the small diameter between the tire and lip, gradually work your way up to the thicker part of the bat. Use the tire to roll the bat past the lip.  Makes a mess of the bat, but there are tools you can buy (maybe rent) that do the same thing.