Because this is a universal gas tank, some alterations to the frame may need to be made. However, being a universal tank is what makes it so great, as it can be used in a number of situations. In this case, Sam's '53 Chevy truck has an aftermarket crossmember to mount coilover shocks, which prevented him from being able to mount the tank between the rear crossmember and the rearend. In order for the tank to fit, he had to make some room, therefore the bottom inner lip of the rear crossmember needed to be trimmed. The piece you see lying on the ground is what was trimmed away to make room.