I helped a friend put one in his 71 Dart and we had to cut the hump and raise a section right under his bench seat 2 inches to keep the pinion angle right.
I thought but don't know (That's why I'm watching) that it fits with some hammering in part of the hump. Then you have to set pinion angle at rearend by shimming or perch relocation? I'm contemplating putting one in my 68 340/4spd.
