Hi Grodon
You may be surprised, by the original booster, both of my C60 have their original boosters and in both cases all that was required was cleaning and replacement of the bellows to get them working well. One of my trucks had been sitting out in a field for years when I got it and was in sorry condition. (As the photo below shows) I did find an NOS one years ago that is my spare if one of them starts to go south.
Because of the linkage design and design of the booster the health of the booster is readily apparent if you have your foot on the brake when starting the engine. The only part I have found to cause problems is the vacuum check valve which is in the line coming from the manifold and there are modern replacements for these.
I bench tested the booster unit, wish I could find my notes on how much boost it actually adds, the design of the booster and the linkage is such that your full foot peddle pressure goes through to the master cylinder with the booster adding to that. One of the particular things I was testing for in bench testing was bleed down time.
I agree about wanting to be sure of the brakes, my drive down the mountain road this weekend it wasn't the booster that concerned me but not wanting to discover brake fade would occur on 6 miles of 8+% grade on a winding narrow road. I just followed the old truck dictum go down hills in the same gear you needed to go up. There were several full stops coming down and the truck stopped without effort.
But please do keep us posted on your progress and what you do on the brakes. Bye the way do you need to reline the brake shoes?
To add to the list of possible booster units take a look at
http://vehiclesofvictory.com/buying-...tion-to-parts/ main site
http://vehiclesofvictory.com/ This is where we found two NOS CMP boosters years ago for $75 each, they didn't know what they fitted. (Yes they are both gone now) but you never know might be worth asking.
Cheers Phil