not sure you can do it the way you want, the sig-stat type hazards work by changing connections internally when you pull the button so power goes to all 4 lights, otherwise you do need 2 flashers ....
here's the factory signal wiring schematic - you'd need to splice into the wires to the 4 corners in a way that there would be no feed-thru during normal operation .... or you could look for a FlareStat [by SignalStat] 105 kit
like this that adds a separate hazard function, show upon eBay regular - still needs to be spliced in to the existing system
Bill
