Check out WOFs templates, they are your friend here, measurement (2) is approx 8 inch.
I think the scope is 10.5 inches to give some point of scale.
According to a template for the flashtube (3) that totals 10 inches including what's inside the barrel, there is a thread here somewhere about the flashtube, should give you details as someone was making them?
As LF says the differences between the two versions can't be that different and as far as the Webley part goes they are not, hope that helps