I have a 1946 2 ton with a 1958 261 (Block Serial Number - 3759365)
I drove it yesterday about 50 miles on the freeway and watched the oil pressure drop slowly the whole way.
When I finally arrived home it was zero.
It never knocked really bad.

I put on another oil pressure gauge and it also registered zero. Normally it pegs the stock 30 lb oil gauge in the truck.

I disconnected the gauge and just had the oil line exposed. It was spitting oil and air but never really poured out oil. The dip stick read full.

So I pulled the pan today. There was a lot of metal in the bottom of the pan. I guessing I have spun a bearing, but have not disassembled to fully diagnose.

Here is a short video of my oil pressure while I drive
https://drive.google.com/file/d/0BzghoG21YVYEeUxyR1k5X2VyelFfWlF2a1g3dFU5eUJSRjVv/view?usp=sharing

I have a couple of questions:
1) If I need a new crank, the casting number 3701488 fits 1953 - 1962 Chevy 235 & 1954 - 1962 Chevy 261. Does anybody sell new cranks?
2) Im seeing a few folks who sell remanufactured ones. Are these OK?
3) Since Im rebuilding, I also had a compression question. I have an 848 head on this engine, most cylinders are about 150PSI, but 2 are at 130PSI. Is 150 what I should be expecting?