My '54 Merc 256 has a leaking vacuum advance canister. It works a bit, but won't hold vacuum. I have a N.O.S. '55 Ford distributor with a N.O.S vacuum canister (smaller diameter than the '54) and was wondering if the '55 unit (distributor and vac. canister) would be compatable with the '54 Merc's Holley 4V carb. Do the larger diameter '54 vacuum canisters have different ratings than the smaller '55-'56 canisters? I found a N.O.S. '54 canister at Hershey but the vendor wanted $100.00 for it which I felt to be a little much.  Thanks : Bruce