for rpm just wrap some wire around the spark plug ht lead, 4 coils should do then set your equipment to measure the rpms trial and error comparing to the rpm displayed on speedo may be easiest HOWEVER ONCE YOU HAVE GOT IT WORKING DONT CHANGE THE AMOUNT OF COILS AROUND THE HT LEAD AS THIS WILL CHANGE THE EQUATION SINCE THE ELECTROMAGNETIC FIELD IS CUTTING THROUGH MORE WIRES INDUCING A LARGER CURRENT...As for speedo it depends on your circuit are you using a microcomputer or just adapting a pushbike speedo if using a microcomputer (coded in hex) calculate the distance for 1 meter, convert to miles and then take the number of turns taken and.. i hope you get the idea as for neutral light just tap off the existing one
What are you trying to make for it? Sounds like a gear position indicator to me, I did the pickup und for mine by adding extra contacts to a spare neutral light switch, cost £5 off ebay, not yet done the display but the switch shows good on a multimeter and more accurate than a rpm/speed comparison.