I used a 15amp 12v-6v reducer for the wiper motor which works well.
The 6v starter was fine for around 9 months, however hot starting was a problem whilst in France for the 80th rally and the starter eventually failed in the rally field so I now have a 12v one fitted.
You may get away with a 6v starter motor for years, others have, it all depends on how often your starting the car.
The TOC Spares alternator kit is simple to swap over from a dynamo as all the fixings are in the correct place. You can do it cheaper, but would have to cobble together part of the top stay bracket.
Also, the standard pulley supplied is on the large size and as the engine is slow revving compared to modern cars it’s better to source/have made a smaller pulley so full charge kicks in faster, around 70mm is ideal but then you need to use a ‘notched’ fan belt as the diameter of the pulley is too small for a standard B section one and they will start to break up fairly quickly (well mine did)
Anonymous