https://www.wikihow.com/Bleed-a-Master-Cylinder
Here is a step by step instruction program that explains how to bleed a master cylinder and the entire brake system.
You might consider this sealant
https://www.permatex.com/products/gasketing/gasket-coatings-sealants/gasket-sealants/permatex-permashield-fuel-resistant-gasket-dressing-flange-sealant-2-oz/
The website has a store locator included so you can avoid USPS delays.
Wildfelr,
Have you seen this on the SDC forum? It could net you a new pump delivered to your door.
https://forum.studebakerdriversclub.com/forum/your-studebaker-forum/tech-talk/71852-avanti-ii-power-steering-a-tale-of-two-pumps-and-four-hoses