Please help small to big bolt pattern

With rear disc's and BBP you will widening the rear track on a A-body Spec 8-3/4. Most off the shelf BBP axles use the 2.5" flange to axle spacing commonly used on non-A body 8-3/4's and Mopar Car Dana 60. Discs will also add another 1/8" per side as the disc is thicker than a drum.

I can almost guarantee a 8" wide rim with "0" offset will not clear your outer fender wells rolled or otherwise with the above set up on any 67-up Dart. Lots of guy use 94-2004 Mustang spec wheels because of this. With the same setup above, I run a 17x8 with a 5.25" back spacing. 5.5 would have been better but it clears with a slight fender roll. Plus I have a rear sway. I always suggest you measure your car to be sure this fit your car.

What rear do you have now or are going to use?