So I started my rear end housing / gear swap on my 78 today. I got the old unit out. Oddly, it went easily. Nothing was really frozen. Turns out the previous (original) owner had this car undercoated. God bless him, if he's still alive!.

I was going to strip it all and POR the car.. but, this has lasted 30 years with no rust issues, so I figured a clean up with a wire brush, and another dose of some undercoating will work fine. I managed to get a 2" deep pile of dirt from the body, and I'm only working on rear wheel wells and the frame/floor section directly under the rear axle.

These 2.47:1 gears in the car really suck right now. The car will not break the tires free.... even in the rain.  . I'm putting in a rear housing I had POR15'd for my Elite some years ago, along with 3.5s with a posi section and rear discs from a Ford Exploder, errr Explorer. It's only 28 spline, but, I think traction will be my problem before breakage anyway, by the time I am done.

I had undercoat in my hair in in places I didn't know I could. 

First pic is "before"

Second pic is "After"

At least there's no rust.