i am trying to figure out where to hook the tach signal wire (sunpro tach) on the distributor for a 1985 monte carlo ls with a 4.3 v-6 if anyone can help me it would be greatly appreciated

My friend did this to his 85 MC 4.3 which is a POS. But heres all I remember. It was hard as hell to find the wires you had to hook em up to. He opened the hood, and under the Air filter is the fuel injector thing. And right behind that, are 2 SETS of + AND - WIRES. He hooked the wires from the Tach to one of those but I dont remember which. Sorry