narrowing a b-body rear

LOL, sorry about the bad link. I just went and measured the housing, flange to flange and it's 54 1/4. According to the moparts list, if it's right, that makes it a 65-67 housing. The reason I would like it narrowed is because I, or anyone if I should end up selling it, would have a greater option of wheels. I hope anyway. I think I will need new axles because the ones I have, the splines are back cut. It narrows/thins down right after the splines, which means I cant shorten them down, right?