Larry 58 burb In 1967 my first AD truck 283 2x4 was overdrive,I never used a kickdown switch,had the kickdown on the dash. Put tension on the driveline,punch the button would downshift very gently pass another vehicle let up slip right back in OD. You don't want to open your 2-fours to downshift. If you get on it best to put it in direct mechanically. I ran the wheels off of that truck,drove it 70 mile round trip daily,gas war price was .17 cents. They act like the wiring harness is such a battle,any older auto repair manuel has the diagram it's about 3 wires. On the 4-speed saginaw over drive,built one of those in about 1970 worked fine. there is one in my 52 3600 out there inthe shed right now. Also had an overdrive unit built at home that went in like a brownie with 2 yokes ran the wheels off of it too !!