I'm not 100% positive, but I believe it is just the difference in hose lengths. The PCV ports are in slightly different spots on the intake between the 5.3 and 6.2. the cans themselves mount in the exact same location.
You were able to trade in a truck with $24,000+ collision damage before it had even been repaired? Wow, that sounds like a dealer desperate for some inventory!
Did they give you fair market value assuming it makes it out repairs o.k.? If so, did you take a hit on value with the major repair? What if it ends up being totalled?