I went with the goodmark 2" wider inner wheelhouses as my old ones were badly pitted. It's 13" from wheelhouse to guard lip (before any pumping or rolling) at the top centre.
265's will fit easily with stock width springs and give me plenty of room under there.
Didn't notch the frame and I've still got 1.5" room at the rear if i ever wanted to relocate the springs or fit a 4 link. Notching would have given me about 4 inches back there but require engineering.
I have only ever carried out the mod the TA way. Move a stock inner to the rail (at the front) and then made the outer as a hoop before making the TA bubble in the rear arch.
Pics are in my photobucket page under 68 AIX Mustang. It has a TCP rear end so the spring side of the discussion is irrelevant. Car ran 12" rears and 11" fronts.