235 truck engines were low pressure through 1953.
0 psi is, of course, low (you can go no lower). Put 20-50 oil in your vehicle and see if it helps. Do not high-rev your engine as a pre-caution. You might get some pressure out of dropping the pan and checking to see if there are rod-bearing shims to be removed. I will not tell what I was told to do with the rods in your situation, when I worked in a shop in the early 70s.
