Change from 4-speed to 3w/OD

grew up working on dad an g'pa's big trucks, what i lernt on, wrench'in and driving! been in a few,..rebuilt 13 speed back boxes few times...but far from expert!! really better at driving than wrenchin on them! takes skills to speed shift a rto 12.5-13!!! makes shifting a 833 a walk in a park!!
Except old stock ones, with worn out external shifters, and those rubber shift rods, you gotta be on your game with that junk.