Here are two very informative
sites about the process. Link
The casting 3232-656C is
correct for the (English AP) Lockheed servo fitted as original
equipment to the 1750 Berlina GT Veloce & Spider Veloce,
listed as January 1968 onwards.
Repair
kits for this type are still
on the market. Pls see www.powertrackbrakes.co.uk who
are very supportive. The rubber membram should say 3818-411 and
the main piston is 5/6 or 15.875mm. It is a good idea to get a
new air valve too and replace it at the same time.
Please scroll down to see the
step-by-step procedure.
Thanks