In 1964 when the engineers at Chrysler were stuffing the new 426 Race Hemi into the Dodge 330's and Plymouth Savoy's, they ran into a clearance problem with the Hemi valve cover and the passenger side shock tower. Since the engine sits slightly off center of the car this valve cover clearance becomes critical with a hemi engine installation.
What the engineer's did was to "invert" the area of the tower where the shock absorber stud comes through, thereby lowering the stud away from the valve cover. They also cut a large notch, or hole into the tower horn at the bottom front just above the frame rail. With this new notch and the lowering of the shock mounting area you could now remove the passenger side Hemi valve cover without having to unbolt the engine mount and raising of the engine. These changes in the standard design made it much easier for racers to pull the valve covers during a race event. This inverted tower and accompanying notch were used on all but the first four or five 1964 race Hemi cars and on all 1965 model race Hemi's.
I have seen different ways people have inverted the tower but a factory job is pretty specific. Once you have seen an original inverted tower you will notice them right away. I am looking for factory documentation regarding this inverted and notched shock tower changes, so If anyone out there has paperwork regarding this subject please contact me through this website.