Transmission Swap: 60's through 90's Ford using a ZF5 speed manual
If you have a 4 speed manual or 3 speed automatic, swapping in a 5 speed manual is something to seriously consider. The earlier transmissions were tough, but they simply were not designed for the torque the Cummins produces. Their input shafts are smaller, the clutches are smaller, and without an overdrive you may have to wind your Cummins to the sky to reach 65 miles an hour.
Some guys say the Ford ZF-5 is a better transmission than the Dodge NV4500 and others say just the opposite. That debate aside; from a conversion standpoint the ZF is better the following reasons.
1.) Easier to mount: In most cases, no modifications are needed to the Ford cross member to mount the transmission.
2.) Easier speedometer connections: The Ford speedometer is cable operated from the transmission or the transfer case, most newer Dodge transmissions however use an electronic signal, posing additional challenges to work through.
3.) Less drive shaft issues: The Dodge drive shaft has a large balancer right behind the transmission. When this is left on the drive shaft, there is an interference point on some of the cab structure. Ford automatic to Ford manual drive shaft yokes are often the same or very similar- but Dodge yokes are often different, requiring more drive shaft modifications or odd-ball U-joint combinations.
4.) Less transfer case issues: Ford transfer cases work much better with Ford transfer case shifter holes and shifters. The NP205 is highly regarded as a "Rock Crusher," transfer case that don't get better unless you spend large sums of money.
After all the smoke clears here's what we've found. By the time you change drive shafts, adapt the transmission to the Ford transfer case, make a custom transmission mount; you're definitely Time & Money ahead by using a ZF5 rather than the NV4500. If you don't care about full functionality with the factory look then this may not apply.