C Body Dana

So why shouldn't I narrow my c body dana to fit my 70 swinger project? This is a budget car and I own a dana 60 with 4:10 posi in it from a chrysler 300. Looking at the cost of a a body posi either dana or 8 3/4 it seems likely narrowing the one I have is the low budget route. I don't know much about rear axles etc, so thought I would ask if I am buying problems down the road? Any thoughts out there on this subject, or perhaps a reference to a previous discussion?