'76 temp sender wire

[maxreps]

Could anyone identify which wire should go to the coolant temp sender? This is due to a recent engine swap and have 2 possibilities for the correct sender wire. both are green. 1 comes from the passenger side along the firewall (no voltage when key on) and the other from the drivers side along the firewall (batt voltage when key on). Initially I hooked up the passenger side wire thinking it was that one. But no temp registered on the guage. So i figured it was the other one but checked voltage before connecting, and found battery voltage. I have not tried it because I dont wanna ruin anything.