Reply To: 6 to 12 volt conversion.

12v Alternator, CTA in Holland do a full kit with bracket etc. it’s a straight swap for the 6v dynamo and throws out double the amperage of a dynamo but not cheap: http://www.ctaservice.nl/product/14266/dyn-wisst-12v-75amp-steun

12v to 6v reducer, I have a similar to one of these https://www.amazon.co.uk/DIGITEN-Waterproof-Converter-Regulator-Module/dp/B018LFV0S6  fitted to my car for the wipers (which I upgraded the arms and blades for)

It really depends on how much ‘wet weather’ driving you envisage doing (I do try and avoid it as wipers are only 1 issue, a lack of demister is another)

As for running a 6v starter on a 12v system, well it may be fine for years, but any weakness in the motor could leave you stranded as I was at the 80th out in France until we managed to do a deal with another member who had a spare 12v starter, but those are becoming hard to source unless you go for a modern replacement like https://www.autoelectricsupplies.co.uk/product/1517/category/217

It really does come down to how deep your pockets are, how and how often you are going to use the car as a lot still run fine on 6v.