If yours are 3 ohms, I can offer the Resistor Pack (1 ohm) to help get them up a little bit, but the 3 ohms + Dyna S is death to the 550 electrics, even with a stock headlight. We have many sad stories of that here in the forums.
One day when I'm not chasing parts for everyone's rebuilds...I'm gonna solve this alternator issue for the 500/550 crowd. There is a way...