That's a good question Greg! My friend swears by Delco Remy gear and shaft lube pt #1960954. Personally, I use Castrol Pyroplex red grease. It doesnt run off with heat and stays tacky.
Finally able to dig these out of the archives. Here is a pic of the factory 1969 shifter linkage for Duane. lever on the left is reverse. Middle lever is the 1-2 and the one on the right is the 3-4
I wish I still had the back drives... I think I had 4 or so here for 69's. The only part I was NEVER able to find was the top backdrive bracket that bolts to the trans. I was able to track a few down on the defunct "Real Olds Power (ROP)" Oldsmobile board.. For the 68 Cutlass/442 4 speed cars. I thought they had asked $200-$250.. Then DL reminded me it was $400-$450. NO WAY that little piece of metal is worth it.. Anyway...