Busy as usual, managed to get a few things done though. Wanted to get the backdrive linkage working to lock the shifter when the car is off. Not an easy task with the different transmission due to the location of the shift shaft between the T-400 & 4L85. Managed to make something from the existing linkage by straightening up the hook end, adding a crank lever, & installing a 7/16" I.D. oilite bushing in an adapter plate I made out of aluminum for it to rotate. A couple of heim joints I had 'in stock' (as Tom would say), and threaded a piece of rod to join them. Seems to work fine for the intended purpose.
Original backdrive rod:
Parts to make it work: