1924 Big 4 colonial questions

Hello, I started the restoration of my 1924 Big 4 colonial with the intend to have her back on the roadfor her 100th anniversary (latest). So some questions arose:

1. When I bought the bike the top fork links were replaced by ones from a later Norton fork. The bottom ones were there so I got this size for reproduction. What I need is the correct distance of the holes in the top links (center-center). Does anyone have a clue about this, or can tell me where one of these Big 4 colonials might be so I could get in touch with the owner for help?

2. What would be the best choise of the size of the engine and gearbox sprockets for solo use?

Thanks

Kurt Linden