I rebuilt my pump, it isn't too difficult, just a bunch of stuff in the way...thats what takes the longest. I got my parts kit from the dealer back then, paid through the nose...Partsshop ought to have it for nearly half that amount.
My pump symptoms were a bit different though, I could not get vacuum at idle, only when driving after 30-45 secs or so did I have enough vac. to brake once or twice.
Have fun! -Larry

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03/83 300D 184k
07/73 280 160k
-88 other 157k