Nigel, your query seems to have been admirably answered here but perhaps worth mentioning that the Vintage Motor Cycle Club have all the ex-Amal carburetor spec and build cards (going right back as far as I could tell).
It is possible to search by carb number or by bike model / year where there was a deviation from an off the shelf item.
It's a wonderful resource, made all the more useful by the VMCC's policy of making information as freely available as possible
