You can add your own flash sync to a Packard. Just get a micro switch with a long actuating arm, glue it (I use 2 part epoxy) to the Packard on the same side as the cylinder, position it so that the cylinder/arm contact actuates the switch at the position of full open. Works like a charm.
Actually, I glue the switch to a piece of thermoplastic and attach the plastic using existing screw holes on the Packard. Easily reversible if you decide you don't want it there. Best to get a couple of Packards, one with and one without the flash sync.