Wiring an aftermarket rev conter into a Nova

Hi guys a bit of advice please.. Am interrested in wiring up an after market rev counter into the 1.6 engine (which has the coil incorporated beside the cam shaft) I am guessing that I should connect the trace wire from the rev counter to one of the four wires on the plug that connects to the side of the coil unit. The car is a rally cross car and is only used on the track so mounting to the dash top etcis no drama. Any advice is really helpfull. PS the engine we transplanted from an astra 1600 si (goes really well too). Mick :)