The 6.4 is lower compression than the 5.7, that's why I put eagle heads on it, they take 10 CC out of the combustion chamber. Also both BGE and SRT8 6.4 cams has slightly more duration so I used a 5.7 cam to give it a tiny bit more time to push on the crank before the exhaust valve opens and the intake valve closes a tiny bit earlier to build even more cylinder pressure. Also the 6.4 uses EGR and the 5.7 don't so when you put a 6.4 in a 5.7 truck you get a free EGR delete.

I am going to sell this truck and build an engine for my newly aquired 2015, going to put in SRT8 pistons and zero deck em, BGE heads, 5.7 cam for real high cylinder pressure and hopefully keep it out of detonation. If I had access to e-85 I would run the SRT8 pistons, zero deck em and run the 5.7 cam and eagle heads for super high cylinder pressure. I think this would be hands down the cheapest way to run a 3/4 ton truck.