Upload & Sell: Off
580 was on 5Dmkii to trigger 430exii, I dont know if there is any other mecahnism from 5Dmkii to trigger off-camera flash (which is bit of lame - considering even EF-S mounts with pop-up flash gives you lot more flexibility to trigger OCF). If I'm missing something here please tell me. I can use a trigger, I've got Apurture triggmaster which I'm not too fond of as it gives only trigger and no other control of OCF. With 580EXii mounted on hot-shoe I could control some aspects of OCF from camera.
You could use a long (16 or 32ft) OCF cable that will let you use your flash the same way as if it would be mounted in the camera's hot shoe. Search for "OCFGEAR SYL ARENA". I prefer the TT1/TT5 pocket wizards especially if you want to use more than one light directly for your setup - with one light and not with too much foot traffic around you, the long cable is the fastest and more simple setup.