Since I wanted to keep the rotating beacon, I added the red and blue strobes to the left and right top of the backbox ($25 on Ebay)
Added a simple automotive relay in series with the existing automotive relay that triggers the beacon. Supply voltage for the LED lights comes right from the power supply board 12 VDC test point.
Later I borrowed an LED from each of the strobes and added it to a police cruiser mod on the playfield. So now I have the rotating beacon, alternating strobes and alternating red/blue LEDs on the playfield police cruiser all coming on at the same time. Sweet.