current handling of diode?

I want to hook up my headlights to my alarm but each side has thier own wire, so i'll have to energize both. I want to do this using one relay. So to do this I am thinking I can just use diodes to isolate each headlight wire when I'm hooking them up to the relay. However I'm not sure as to how much current will flow therefore what rating diode I should use. The bulbs are 9007 so they are 55 watts each. Now what I was thinking is that each bulb would use about 4.6 amps (using P=VI). Assuming this formula applies, could I use 2 3-amp diodes in parrallel so that it would handle 6 amps and be enough to handle each bulb?

I would have to suggest buying a higher amperage diode. I have not diode isolated a headlights  but I use 10 amp diodes just for parking light isolation.