Here are some pictures of what I did to my '69 4020. I took these pics after i just temporarily mounted and wired in one ballast on one side just so you could see the difference. I used the flood light Par-36 enclosure ($18) from duckworks aviation  and a normal ballast VVME H3c 4300k HID kit. The biggest issue with the install is the length that the plug sticks out the back of the HID bulb, there is very little clearance but it works, looking at the set of DDM h3 bulbs that i have laying around i would think they would fit also but they are just a fraction longer. My camera battery died before i could take some pictures after i rerouted and hid the wiring but after i took these i drilled a 1/4 hole through the metal housing of the lower back of the light so i could get the wires out of the housing and back to the ballast. If you dont have the tool or a really small screwdriver to take the tyco plastic terminal ends off of the light bulb wires you will need a bigger hole to get them through. Feel free to email me any time if you have any other questions.

http://www.duckworksav.com/Upgrades.html#Round%20Enclosures