I'll be starting on a TH-700R4 to SM-465 swap here this weekend, FINALLY.
The hardest thing I can forsee will be placing the bracket on the frame for the mechanical clutch as far as mechanical things will go.
I will look into getting the proper ECM chip if there seems to be much of a problem with the ECM wanting to lock up the torque converter and setting a code or causing a driveability problem, but that will come after the swap.
I am also swapping out the 2WD auto trans, for a 4WD manual and eventually swapping the rest of the drivetrain components in stages to complete the entire swap. Kind of nice I have had and eventually parted out nearly 35 of that generation GM trucks in all shapes and sizes over the years.
I also have the 465 shifter on the bench doing an upgrade to tighten the sloppiness between the handle and insert, I am considering taking a few pics along the way.