If you don't want it.....
Our old 948 cc Cannon manifold (the car isn't here at the moment) does not have a vacuum connection, and we've driven it that way for (off and on) years. The Warneford manifold one the 1275 project has a roughly 3/8" tap on each intake runner (one with a bolt blocking it off; one sans bolt; I haven't checked the bolt size) that could presumably be used for a vacuum connection to the distributor, with various adapters etc.
Apologies, but I can't provide any wisdom. I've got David Vizard's book on tuning the A series and will follow whatever he says regards connecting the distributor to the manifold. Otherwise, would have to follow up on trying to find someone who could change the weights on the distributor to convert it to purely mechanical advance. Or convert the whole shooting match to Megasquirt EFI and pure digital ignition.....