Following the idea on Strobist, I add a sync port to my 580. I took some pictures during the process, hope it can provide some visual images for someone want to try it.
It’s a pretty simple mod: get a 1/8 mono phone jack from Radio Shack, unscrew 4 screws at the bottom of the 580, unplug the only one cable, drill a hole at the side and stick the phone jack through, solder 2 wires to the center and side pin, and finally tighten the nut outside the flash.
I think the original concept was to use the port to connect to the PW. Since I don’t own a PW, I use it to connect to my L358, or simply for triggering the master unit without having to push the Test Button while metering.