I have a 99 camaro 3.8, when I originally got it my plan was a LS swap it had set under a tree for 3 years no interior etc. I traded a gun for it and got it on the road, few months later the motor blew and it was before I had the funds for my planned build so I went with a 3.8 from jasper crate engines and it runs good. Now I want to do something different I know how much of a pain the 4th gens are I replaced the motor my self and have done all my work on it alone.(I worked as a diesel mechanic) which is why now I want to put a 6.6 Duramax under the hood I know it will be a lot of work and time but that is fine. Any recommendations where I should start?

 

A tape measure? 4th gen engines are very shallow and it has the windshield above it. Even a basic small block with a carb on it is too tall and requires a saw and a tall hood scoop. Keep in mind your inner fenders are structural. Also this is a unibody car so it is just sheet metal no real frame so everything from motor mounts to how to the rear will need re-engineered to handle the toque. IMP you project should be done on a car with a frame that can be boxed in a stiffened up.