Bit late now I guess but you should check out Tinmantech in the US. Says a lot about aluminium welding and eyewear. Am in the slow process of building a S1 Eleven replica although I prefer the word clone. Am endeavoring to make this as per original down to period NOS parts where possible. Aim is to make it a known recreation of an Eleven to use on the track in anger. Long way behind where you are at. Can answer one question you asked. The rear dynamo tacho drive was a Lucas supplied back plate and is no longer available. Crosthwaite and Gardner used to make replica castings but last time I looked they no longer supplied them. Like most things C&G they were expensive and I didn't buy one. Wish I had now. Just joined to contact you about things Lotus and Eleven.