Just for clarification/confirmation. My rear is from a 1974 Nova and I did the conversion. Was a direct bolt-in fit but driveshaft needed to be shortened. I measured overall width narrower than my 8.2 bird rear by about 5/8 inch overall...which moves the wheel inboard by less than 3/8 inch on each side.
I do believe you to be correct craze, very minimal width lost and lots better then a half inch in on each side. Are you measuring from the outside of each brake drum or flange to flange? I believe Firebird 8.2 should be 55 1/4, at least that what has been told to me. And yes, I also had to take one inch off my driveshaft also.
