Head number

[Kube]

Jmujica, the 59AB head was designed to be used on either the right OR left side of the engine.
There is no need to replace the nuts unless the threads are corroded or you simply want freshly plated nuts for appearances.

Washers? There should be no washers unless you have aluminum heads.

There was truly an interference fit designed between the studs and block. Many have made the mistake of running a tap down the block with subsequent issues from doing so.
Unless you break a stud or one (or more) comes out with the nut, there is no reason to clean the threads in the block. Even if a stud does come out, do not chase the threads in the block.