Im guessing the revs is being done digitally already, but the speedo looks to be cable to the gearbox gear thing, all mechanical. Unless ive missed something? It looks as if you can get a plug the goes on the end of the cable, converts the revolutions of the cable into a digital signal which you can then calibrate. Im currently reading out by +10mph.
Sent from my GT-I9505 using Tapatalk