Jake; The 65 Ranchero rear end I have is only about 53 inches wide, sorry.
But after checking you can use a full size ford truck rear end they run at 60 inches.
I'm imagining that's a heavy metal car, so you will probably want a 9 inch rear end so nothing is breaking on you. So here is a good site for you to review, for your own benefit.
I would pull the axle's before I bought one, to try to get a 31 spline for strength.

http://www.maliburacing.com/ford_9_i..._nine_inch.htm

Hope this helps. Kurt