[55-72 GM trucks]

you can do that but it will hurt the collector value because every serious collector of Napco trucks knows GM never let one come off the line wit anything but a 235. Now, if yours was born a 2WD off the line and bears a regular non-4x4 7500 lb tag and was later upfitted, then you are good to go but thats because of the differences in transfer case shifter and related hardware and rivets vs bolts and so on.