I have recently done some reading on headlight systems and their history. As you know the 50s trucks had 7" sealed beams. The 6 volt bulbs are rated at 35/40 watts for low beam/high beam. However when they went to 12 volts, they made available 55/60 watt halogen bulbs that have the same contour and are an exact fit. They are actually pretty good lights, the same as the ones Cleitis mentioned. Now how can you accomplish this with a six volt setup? Here is how:
They sell bulb assemblies that take an H4 or 9300 style bulb and are very similar looking to the stock sealed beams. They also sell a 6 volt halogen bulb that is rated at 55/60 watts. I just purchased this set.
6 volt 55/60 watt headlight . They are a very close fit. I think I will need to trim a little of the metal on the inner bucket hole to make room for the rubber seal on the assembly. I can put 12 volt H4 bulbs in these if I want and I think I will go to 12 volt anyways. If you use these with 6 volt bulbs you will want to put a relay in the supply after the headlight switch. At 60 watts they would be drawing 10 amps each.
I don't think there is a kit to convert 9300 H4 style lights to HID. I think the idea with HID is to use a complete setup made for the HID bulb.