I worked on the 392 crate motor project. I will give you a few things I know. The cylinder ports are freer flowing in the 6.1 and it requires it's own intake to match. The 6.1 cam is more aggressive than the 5.7. The block is physically the same size but has much bigger bores. The 5.7 is 3.92 inch bore while the 6.1 is 4.06. When we did the 392 we increased the stroke to 3.79 and utilized the 6.1 block for it's bigger bore; so essentially the 392 is a stroked 6.1. Most of the architecture is the same or very similar. I believe the combustion chambers are a little bit larger in the 6.1 also. The 5.7's come with MDS whereas no 6.1 ever has. The Challenger's 5.7 will NOT have MDS when ordered with a 6 speed as has already been posted. Get yourself a Mopar Performance catalog and you can see a few of the things that are currently available for new HEMI's. Expect more when the Challenger full line hits in the fall. Hope this helps.