Rear End

I have a 1966 Dart I am restoring it had the 170 slant six in it, I am putting in a 318, with a 727 Trans, but trying to figure out which rear end is in it, as there are no visible markings, and can I use this rear, or do I need to find something else, and idea's? Any help is greatly appreciated...

Thanks

727's do not fit without mods in an 63-66 "A" body.