I have 15x7 Rallyes on the back of my Wildcat. I can't account for the shape difference of an Electra rear wheelwell in comparison, but I do know that a 15x7 won't clear the brake drum without a spacer. I have 1/2 spacers on mine, but I believe 1/4 will clear. I believe 1980s full size station wagons were the source of these wider wheels.