The 6.4 timing cover sticks out about 1/2 farther than a 6.1 because it has VVT. You can't bolt on a 6.1 cover on with out changing cam, timing chain and crank spacer.Anyone running their kit. I picked it up for my 2015 drop out 392. So they are now telling me I need to put a 6.1 Hemi timing cover on to make the kit work.