72 318 Scamp. Low oil pressure 1 minute after startup.

The pictures of the block shoes a lot of junk in the passages. I would probabally pressure wash the block as best I could and blow it out with air. Any possibility of you stripping it down and having a machine shop clean it out for you? My machinist will hot tank and install new cam bearings and freeze plugs for 150.00.
Depending on your use of the car, a stock 340 or 360 cam. Probabally would not go any larger than a summit racing .454/272* .050@216* cam if it were me.