The Stovebolt Site Forums The Shop Area Driveline 64 rear end

1964 is not a dropout style.
1955-62 1/2 tons are the only dropout center sections that will fit in the 1940-54 torque tube axle housing to replace the torque tube.
One thing to think about is your 49 has Huck brakes, the 64 has Bendix. Putting better brakes on the back without upgrading the front can be a dangerous proposition. You should at least swap the front over to Bendix at the same time or install an adjustable proportion valve on the rear. You do not want the rear to pass up the front, on a panic stop, which will happen when the rear locks up first.