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As Jeff noted makes no difference in the trailing bed but the 67-72 trucks share the raised ridge known as Bumpside and will swap.
Don't know why you are wanting make the swap, but want to offer a tip. if you pull the cab & front clip together (front fenders) including doors you can save a lot of time and aggravation with re-alignment. There are 6 mount points to the chassis, 4 under the cab and 2 under the radiator support. You can lift the sheet metal and roll the chassis out or lift it with a machine like a backhoe.