The following information is correct for Ford use Bendix Vacuum boosters. Unsure if Chev are the same.
If planning to restore one of these boosters, you will likely need (or want) to replace the seals within the vacuum chamber. These seals are on the large plunger plate.
A company called
Seal Jet, in Brisbane, Australia, can supply replacement seals for the above application. I have bought these myself and they are correct fit. Details as follows:
Cup 6 & 3/4" No3 $52.50
Felt Ring 5 & 5/16" x 6 &9/16" x 5/16" $30.00
You will need one of each to complete the set. Prices are correct at time of writing. GST of 10% will apply in Australia, unsure about O/S.
Contact Details for manufacturer:
Seal-Jet
Building 1, 350 Lytton Road
Morningside, QLD, 4170
Ph (07) 3899 3266
Fax (07) 3899 3277
Email
Happy Hunting