You can get a '68-'72 center section that will fit the 3/4 and 1-ton axles (provided that they are not torque-tube axles). These had an optional 4.11 gear ratio. They were often found in trucks with automatic transmissions, but mine came from a 4-speed truck. It might be another option to consider. If interested, search the archives as this swap has been discussed several times.
