4 bolt vs. 6 bolt Valve Covers on RB Engines

The RB engines from 1959 through 1962 used 4 bolts to tighten the valve cover.
Below is a picture of a standard 413 4 bolt valve cover.

In 1963, Chrysler changed to a 6 bolt cover when they added bolts to the outboard corners front and rear.

On a few early 1963 engines you will find the transition valve cover. It is 4 bolt cover with
provision for the additional 2 bolts but the holes are not drilled.

Carl Bilter adds: "The 4 to 6 bolt valve cover was a running change during the
1963 model year, starting February 1, 1963. The 300J retained the 4-bolt covers. The K/RamK had 6 bolt covers.