Martin, your 8" booster may be the Gr-3 Pantera brake booster. I installed one in a CA street-racer Pantera back in the '80s that also barely fit. i was told (maybe by Wilkinson) that thanks to someone exceeding his personal skill-set, then running his home-repaired Pantera under a semi-trailer and his heirs suing the distributor, Bendix-Italia immediately stopped selling repair parts. After that, only complete assemblies were available. All 308-series Ferraris and maybe a few Maseratis also use the 8" booster. Never checked the Deauville/Longchamp booster sizes.
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