The front crossmember is different between chevy and gmc. The crossmember can be swapped to allow you to run the 270, but it is a PITA. I am going to assume you have a longbed truck, and would like to assemble a shortbed. I would caution against this approach because the ID number will identify your truck as a long wheelbase truck. It would be better to buy a shortbed truck as far as the title is concearned.