I started on the rear differential. It is a 3.23 open and I wanted to at least put in Sure-Grip unit and replace the half-century-old bearings. I was considering upping the ratio to a 3.55 but after discussing it with Cass at DoctorDiff.com he said to stick with the 3.23's. The amount of change would be negligable. The reasoning was that a 3.23 running relatively short 26.45" tall F70x14 tires will be running almost the same rpms as a set of 3.55's with a set of 28" 275/60x15 tires. A real gear change like a 3.73 or 3.90 would result in some actual seat of the pants gains but I am looking for a crusier not a quarter miler with this build.
So essentially I already have the actual performance of a 3.55 with the shorter 14" tires.
So I am ordering a new Sure-Grip "Powr-Lok" unit and the install kit and axle bearings as well.
https://www.doctordiff.com/8-3-4-clu...-powr-lok.html
Here's the smelly parts after I got eveything out today. The gear lube was dark but smooth. I had a piquant bouquet with thankfully, no metallic notes. The pattern looked nice.
Looks like the gear set is dated 5/21/1970 and a 1971 casting date on the housing. It appears to be a 29 spline pinion - it takes a 1-1/4 socket on the pinion nut.