This is a kit from Summit's catalog. http://store.summitracing.com/partdetail.asp?autofilter=1&part=AMC%2D509102&N=700+311187+115&autoview=sku Very easy to install. And almost as easy to make yourself.
There is a lot of good stuff on Ebay, but you need to be carefull of what and who you buy from.
This is what you should get: http://www.datsunrestore.com/catalog.html
Datsun 240Z 260Z 280Z H4 Light Conversion Kit
Bright White 60/55 Xenon Bulbs & 7" Housings Kit Converting your Datsun sealed beam headlight system gives you a whole new range of lighting options. Instead of the limited choices available with sealed beams headlights, and the few manufacturers that make them, you will now be able to use xenon bulbs, colored bulbs, any replaceable bulb to give you the look you want! In addition, our housings provide superior beam patterns. The DELTA 7" Headlamp replacements for sealed beam and Halogen headlights feature European lead crystal precision optics with "E" Mark Certification. The "six step finish" reflector provides a precise reflecting parabola. These lamps are powered by H4 Xenon Hyper-White 60/55-watt replacement bulbs, which projects a hyper-white bluish beam that will outperform any standard Halogen H4 bulb. The DELTA Headlamp kit is also equipped with a Rubber Boots to protect the optic unit from dust and moisture. This is a plug in and go kit, no modifications needed. Our housing kits come with: Two glass housings One pair high output xenon super white bulbs One pair of rubber socket covers to keep sockets clean and dry
You Zcar H4 Light Conversion Kit