There are people running 295's on the rear of 68-72 Chevelles. I expect Beaumonts would be the same. However - I think to run the 295's, you'd better have your back spacing bang on, and even then I suspect you might get a little rub over bumps and corners if you don't roll the fender lip. With 275/60R15's, you still need to get your back-spacing right unless you are or want to run air-shocks or other lift system. From my experience, the stock GM rally wheels all had too little back-spacing (if I remember correctly, the 8 inch Vette rims had 3.5 inch back spacing). On an 8 inch wheel, my experience is that the back spacing should be 4.5 inches. That'd be 'zero-offset' and should centre the wheel in wheel well - giving you clearance between tire & both inner & outer wheel well housing.
The guy I knew who ran 295's on the rear had 10 inch wheels, with 5.5 inch BS (again, zero offset) if I remember correctly. He had to trim the shock mount bolt to clear the inside of the wheel. (Note that if you run 16 inch or larger wheel, they clear the shock mount bolt.) He had also rolled the fender lip with a baseball bat. He may have had to 'massage' the bump in the inner wheel well where I think the body mount is.
255's up front are wider than what I have ever tried (245's on 7 inch wheels with zero offset (4 inch BS)). I think the 255's would likely fit but I've never tried then myself.
As always - the usual disclaimers are necessary due to the chance your 40 year old suspension or body is not stock...
-- Edited by 66 Beau on Monday 2nd of September 2013 02:30:14 PM
"So when you spot violence, or bigotry, or intolerance or fear or just garden-variety hatred or ignorance, just look it in the eye and think... The good outnumber you, and we always will." Patton Oswalt
I 275/R15'sw should fit on the back without rubbing as long as you have the right wheels. If you happen to have a '64-'67 rear end, you might be able to get away with stock vette rally wheels (narrower rear ends). Otherwise, check the back spacing and go for 4.5 inch BS for 8 inch wheels.
The 255's should fit up front too - check with Uncle Bernie for what back spacing he has - but be careful, after market disk brakes will alter the tracking width.
