What oil pump to use.

Here's a good read on the M72. I put the M72 on with new MP high psi spring on my 340 build. Disassembled, checked clearances, new MP high psi spring prior to install.
80 psi at 50 mph, 45 at idle. Original 273 adjustable rocker valve train.
Melling M72 Oil Pump Performance Blueprinting - Poly318.com