Overall length of a '54 frame is 173 inches. There are dimensions in the FAM, dated 1-15-54. From comparing the pictures of the end of your frame to mine, I don't think anything has been cut off. But your last picture with the tractor in the background sure looks like an earlier frame. The spring bump stops at the rear arch are directly under the frame rail, while the later frames have a bump stop bracket outboard of the frame rail. Installing a 54 bed on an earlier frame would require raising it to get the wood above the rear arch.
