Hi James - you can get electronic rev counters that will run on 6volts (they are only counting the points closures).
My take on your issues are that it clearly is running way under par.
It should not need any rev counter - waste of money for what you are after, my advice is to join or go to your local Austin Seven meeting discover the local "expert".
Get them to give you a helping hand which I am sure they will, and get the performance right she is clearly way below right at the moment.
Hope this proves useful and saves you a lot of grief.

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