I'd been looking at these, but yeah speak to the guy, ask him if he knows anything about our speedo sensor and if it'll work with these clocks.
If he says about using the disc bolts as pickups for its own speedo sensor then ask if the clocks will show the error codes.
I'm currently running without the speedo on my bike, which is fine, but if you rev it close to the red line the system then registers there's no speedo and shows the 0-4000-0 error codes which only resets when turning the bike off at the key!
Food for thought