Tricky Dick initiated the double nickel speed limit.
One can buy one hell of a lotta gasoline for what it will cost to swap the tranny, and the paltry 2-3 MPG gain will only be on the highway.
And btw: 1950/56 Packard Ultramatic's had a lock up torque converter. The 1955/56 version was such a turd that Packard 'nuts' refer to it as ULCERmatic!
Bill / Retired Ford Parts Manager / SoCal Chapter Member / Part number research: 1928/2001 trucks & 1928/89 passenger cars.
2015 F150 XLT 3.5L 2WD Super Crew