B-Body Diff, C-Body Diff, Wheels/Tires

A 65-69 C-Body axle is 2.25" wider than a similar B-Body axle. You would need an extra 28mm of positive offset in the wheel to make up for that. If you can find a wheel with +50mm of offset, you might make it work to keep a 245 or 275 under the car. Figure on needing a positive 80mm of offset to keep a 335 inside the quarters.

Here's a formula for you - half the tire width minus offset time 2 plus axle width (drum to drum). That will give you a rough idea of out to out of tire width. Don't forget about converting from mm to inches. A 245 on a mustang +24mm rim on a 67 B-Body fits ok, and that would work out to 67.4559". A 335 tire and a 61.75" C-Body axle would need a +95mm offset to fit in the same envelope.