I've got air shocks, so I can get a little more clearance. Im looking at a set of 315/50r15 tires to slap on the rear.

 

You need to get the proper wheels/backspace for the width of the tires used. I would suggest an 8 inch wide wheel with a 5 inch backspace. Not sure if those 50's width tires will fit/clear.

 

I'm thinking you mean 325 50 15. Your going to need a 10" wide wheel with around a 5" back spacing. You do not want to depend on air shocks with a tire that may interfere with the body or chassis at lower heights. Your also getting into a drag radial or a dot tire that's really not recommended for the street.

 

I've got some 2" wheel spacers for the back. The set up was currently fitted to an 80s monte Carlo. As far as use on the road; safety has been thrown to the wind

 

While I agree that some modern things are not applicable, safety items should be at least what was original equipment and NOT downgraded from EOM standards.

 

N50 15

Test fit the tire about 20 years ago on the 67 Cutlass Holiday Coupe that I had at the time. Stock rear end, with 15 x 8 Centerline. Unfortunately I do not remember backspacing etc, and no pics to the best of my recollection.

It did fit with no contact, the car had all new suspension. Definitely the largest tire I ever had on the car. The look was too big for my taste at the time. Although the tires alone looked great !

 

If your careful with the measurements, you can get a 325/50R15 drag radial on the rear. I have a friend with a 66, he ran that size for years. I really wish someone would make that size tire in regular radial tire construction. That tire looked badass on the back of my 69, and his 66. The drag radials don’t last long, and after driving for a while the tires get warm and pick up every rock and throw it against the quarter panel.