Brake Booster, under floor, '77 GMC (gas) info?

[uglytruk]

There is a similar chassis to mine with a nice at the local junkyard, almost new vacum brake booster.This mounts under the drivers step. Mine seems to work ok, but the very helpful yard-man said they are a desirable item, as they rust-out. What should I pay for a spare? Mine doesn't look rusty. :roll

[will_gurt]

From my understanding they rot out from the inside out.

[uglytruk]

How many donneros? The junkyard businness of 1/2 price is kinda' funny, especially when the parts' half worn. I like paying 10%, or buying the whole running vehicle for $100. :guns
Has anybody bought one of these boosters new? Would seem like several hundred $$$.
My tactic is to buy in bulk, as I have about ten crap-cans to feed. It hurts when I pay $125 for a "runner", and then have to pay $125 for four used tires, n/i rims. :cussing