Your bigger problem is that there are only two lights on each side and the Imperial has 3. Sequential lights need at least three or it would look funny. I've always disliked that they didn't make the third one a light and do something else to get reflectors back there. Maybe you could section the taillight housing and lens to make a third one on each side.

Anyone tried that?

The difference in wiring is probably to accomodate the brake light funciton separately from the turn function.