2000 Chevy silverado with a 2006 5.3 vortex motor. will not start

We figured out...we changed the fuel pump and then had to have it towed to a dealer to clear all the security codes...this truck is going to be a pain..The rear end doesn't go to it..the front brakes go to a 2011 chevy avalanche..I'm in for a major headache...thank you for your response :)