540Challenger - Is there a specific reason why you are considering a 6.4 block? I have not had any of the 6.4's in the shop but was wondering the benefits over a 5.7 which seem relatively easy to locate for cheap? Nothing against the 6.4. From what I've read it's the same bore as the 6.1 with the crank having a longer stroke. I also read that there are oiling passage mods but I'm not sure if they are for the MDS or overall improved oiling.
I just wanted to know if there are any specific advantages I am not aware of.
