295 on an 8" rim I feel is too wide a tire. I put 295's on my marauder in the back and widened my rims to 9.5". If you are going to piddle around an 8" would work but if your going to race (1/4 mile) or do spirited driving I'd think otherwise.
A couple of guys have fitted 10s on the rear of a 69 or 70. Zogman comes to mind right off the bat. The key is backspacing. I don't know the exact number. But it was somewhere in the 5.5 inches or even more. I've even seen guys with with as much as 6 inches of backspacing. Problem then lies in whether the wheel of choice is available in that configuration, or if it can be custom ordered.
If you can custom order something, be prepared to wait. Even the big name wheel makers wait until they get a whole slew of custom orders before they shut down regular production and tool up for the custom orders. I waited 8 weeks for my rears and 10 weeks for my fronts. I ordered them at different times during different portions of my build.