Site,
The biggest issue I found with the LED headlights is the way Datsun did the wiring. Since LED's are diodes they only allow electricity to flow in one direction. Rather than the center post being a common ground, the center post is hot and the switching is done between the 2 posts that are ground in the Datsun world. Here's a thread where I asked Dave about his harness and how it's wired. The thread also has the headlights I ended up going with.
Because I've been lazy and the lights are working I haven't taken the anti flicker block out yet, but according to Dave the harness puts the ground on post 3 where it typically is outside the Datsun 240z world.