installing aftermarket Tach

having a little problem finding the wire for the rpm input from ignition coil i kno it is supposed to be the white with black stripe ground wire off the coil but i have 2 solid white wires coming off and 2 green wires i think last i checked so wich of the 2 white would it be if any1 can help.

ok updated now upon instillation of my aftermarket tach. the coil had 2 pink wires and 2 white the ground u splice into for the rpm recieving wire is the largest diamater white wire on the left terminal, hopefully this helps ppl that have trouble installing a tach into their S-series