Alternator Amp Size?

My Duster 340 was converted to electronic ignition in the mid '70s with the addition of the external ECU module (orange box) (mine is actually blue) and the 4 spade ballast resistor (1971 and up).

Does anyone know if I can go back to using the standard/original (1970 type) 2 spade ballast resistor whether I install the PerTronix electronic ignition kit in the distributor or stay with the existing external type ECU (orange box) mounted on the fender?