I have several out of Olds', if that will work for you. Email me if interested: drolds1@bellsouth.net. Thanks, Bob.
They will. TH400 and 4-speed are the same. They don’t have the extra tab for the TH350 lockdown cable. The one in my Buick looks identical to the one in my Olds.
Racebuicks sells the switch, here on the site. Been awhile since I did it, but I think you may need the switch and a bracket for it? Check with Racebuicks .....Jim/Rott