I have a 55 second series on a 76 K5 chassis. We had to shorten the frame up front, build the frame rails for the bed, and build the body mounts for the cab and front end. I also relocated the gas tank from behind the seat to the factory location that the K5 frame had. The rear end also had to be moved back 3 1/2 inches. It was a tough project, but it was worth it. Let me know if you have any other questions. As I am new to this site, and this is my first post, could anyone tell me who I should talk to about info for my 72 Blazer project?