Latest Update:
I'm back up and running with the help of this forum and Loader Parts Source. Thanks Tazza for suggesting them. I worked mainly thru Don of LPS who provided outstanding customer service with lots of follow-up and updates thruout the process. Being a difficult customer with lots of questions, I really appreciated Don's patience. They provided parts that where un-obtainable from Hydra-Mac parts sources and since these pumps do not have the replaceable brass plates for the rotating assemblies, they did a great job in regrinding and re-hardening the cast iron pump faces.
I still have my "test" charge pressure gauge in place, and noted no fluctuation of pressure from the relief valve setpoint, until I shut the machine off! To my surprise, there is a huge power increase too.
An unrelated problem I had with the hydrostatic repair was the worn flywheel to pump coupling. (this machine has pumps stacked in-line with the engine) Long story short, I ended up using a unit from Hayes Couplings, which they ended up making a custom adapter to fit their coupling to my Isuzu 3AB1 flywheel. All good.
Thanks to everyone that helped.
Joe