Thanks for your response. What I am trying to figure out is if a SSM5001/05 (MPH) will work properly with my original 1966 speedo drive. The 1966 Lightning used a SSM 5001/03A, the 1967-69 used the SSM5001/05 with a 1.25:1 ratio. Are you certain the 1966 ratio is the same as the 1967-69?
The parts manuals say that they are the same ratio. I've been interchanging them for a while throughout the model years. Even between twins and singles, triumphs and BSA's and the only differences I've seen is the diameter of the hole in the hub.
That said, I'm not sure it matters too much. Smiths magnetic gauges were notoriously inaccurate when new (up to 15%) and probably don't improve with age.
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
Thank you very much for the information. You covered exactly what I needed to know. I also need to know the part number of the 1966 stock upper triple tree or other equivalent parts numbers that will fit and accept the stock mounting plate for the speedo and tach.