Correct Master Cylinder

[samkost]

Before the start of the restoration of my 1972 C10, I had an excellent full functioning power brake system.
During the restoration process I had a new power brake booster added and installed.
The resto shop turned out to be a nightmare of mishaps and shoddy workmanship.
Ending the relationship I took ownership of the truck and brought it home.
When I picked up the truck, my power brakes were not functioning with a rock hard brake pedal.
At home I started to correct the many inherited issues.
I later found out and determined, with help and questions answered from this forum site, that a shallow short bore piston was installed instead of the long deep bore piston rod between the OE master and the new booster.
I replaced the short piston with the long and partially regained my power brake function but it wasn’t 100% as before.
I went to a new shop to get the trucks brake system checked and bled.
They advised that my present master cylinder was missing an O-ring resulting in some vacuum loss and had a slight bit of corrosion between the master and booster. Strange they were unable to get new replacement parts?

So, I need to confirm the new correct replacement master cylinder part to order is an AC Delco #18M1036.
Is this AC Delco master a short or deep bore?
I also want to replace the proportioning valve for good measure.
I could use some guidance with the bore size diameter, shallow bore or deep bore and a correct proportioning valve requirements.

I’ve added photos of my present set up because of confusion what may have happened from previous owners add ons or past upgrades.
The present master is a deep bore piston and is taller than the new AC Delco.
Is this master cylinder the correct OE part for a 1972 C10 with front disc/rear drum power brakes?
I would appreciate any recommendations and comments.
Thanks all