WIDEST TIRE?

I am thinking a 215 might be doable as is. The early b body rear (flange to flange) is 55". I'm assuming you had a 7.25 in there originally. That would add .9" to each side. I don't know which wheels you switched to with the addition of the BBP b-body rear but just take some measurements and see if you're good to go. You can also ask a shop to mount a 215 wo/balancing it and fit it first.

IMPORTANT: Whether you go the above route or if you want to max out with a larger combination (which will require wheels with the correct width and offset), always take measurements on both sides. Never think that one side is going to be the same as the other. Even though the b-body rearend was installed (but do not know who installed it), like Ma Mopar, many rearends are not perfectly centered. GL.