It would be difficult to get a wire "too large" when powering a HEI system. The resistance of the primary winding on a HEI coil is about 1/2 Ohm, which means that the momentary current flow in the power feed wire can approach 30 amps, before the inductive reactance of the primary windings begins to limit the current flow. At 2K RPM, the current flow in that wire starts and stops 66 times a second. A 10 ga. wire might be "overkill", but it's certainly not "too big" when carrying intermittent current pulses of that amount of amperage.
Jerry
