I put a crate Hemi into a 440 RT Challenger and used the Schumacher mounts. It sat very close to the right tower, maybe 1/2" away. Now I'm doing a 71 Cuda with the 528 Hemi but I've not going to use the aluminum valve covers because of the clearance issue. The show on horsepower tv, I think its Muscle Car Garage did a hemi in a 70 challenger and they said they knew about that problem and said the Chrysler for some reason had the motors off center a bit. They centered the motor and trans when they did their car. All the original Hemi cars I've seen all sit off to the right. Same has the 440's. The right plugs are a lot harder to get to.
But whoever said Mopar should know issues when they sell things sure was right. Maybe that's why so many crate engines had problems too?