It has been my experience with 1951-54 early special Kaisers that when the oil pressure sender unit starts to deteriorate (and they do normally over time, like any electrical device) it will read lower than actual pressure. Do you know for a fact that the sender was replaced at the time of the rebuild? How is the wiring? I know that I gained 15 psi (or thereabouts) on the gage when I replaced the sender on my 1951 Kaiser Business Coupe and my 1952 Kaiser deLuxe. Along the same lines, how is the water temp gage working? My experiences wiith that sender indicates that as the water temp sender deteriorates, it also reads lower than actual temp and will not go above the halfway mark, no matter how hot the water is.
Fords and other cars with negative grounds tend to pin on the high side when senders deteriorate, but as the Kaiser has a positive ground, it will drop as it starts to go bad.