it'll be the white wire comin out of ur iginition harness (i'm pretty sure its white)

to find out which wire it is, plug a tester in to each wire and the one that gets 12 volts when the key is in "on" position, is the one u need to use.

how many wires coming out of the shift light?

i think the green is for ur tach, it'll go to the one of the wires coming out of ur distributor. there's a plug w/ two wire coming out of it (forgot what color they're), but its one of them and u can test around w/ each one. it wont hurt the system. (plug in the green/tach wire to each one to test and see if the tach on the shift light works, ur motor will have to be running)