Daren,
According to my Lucas catalogue, the 1947 & 48 machines were fitted with a Lucas E3HM dynamo (Lucas part number 20019A). Later machines (1949 - 54) were fitted with the longer E3LM dynamo (Lucas part number 20012A).
The E3HM dynamo was paired with an MCR1 voltage regulator, while the E3LM was paired with an MCR2 regulator.
Hope this helps,
Regards,
Eddie.