In essence, that's what I did, but I ended up changing it a little for the luxeons. If they were normal LEDs, yeah that would have worked fine. But with luxeons they like 350mA so there's a lot more power going through them. I wired up 2 lux's in series to use up some of the power, but there was still a lot going through the LM317 so both the LEDs and the LM317 heated up pretty good. Near 100C. I ended up throwing another 10 watt resister in series to dissipate the power to more managable levels. That's what the big yellow thing is in the pics. The LM317 is the black thing on the right. Did you look at the link to YT in my first post? There's more pics there.

When I said the brightness changed dramatically, I meant the circuit that used only resisters and no LM317. With the LM317 the LEDs are steady as a rock. There's no noticable change in brightness even when starting the engine.