Post installation feedback for 2008 XLR:
Parts:
I ordered the LED turn signal and parking lights from SuperBrightLED using the above link.  
Installation:
I will not repeat everything from above, but here are some additional observations.  I found it difficult to see what I was doing with only the wheel turned, so I removed the tire.  Just be sure you use both (for safety) a jack and jack stands.  
The three bolts holding the headlight are easy to identify because they are silver/gray and have large matching washers.
Cracked lenses:
My lenses over the turn signals were partially cracked and melted, but the cracks did not go all the way through the lenses.  They seems secure for now, so I left the lenses in place.
Hyper-flashing turn signal:
Even on my later 2008 model, I got the hyper-flash with the LEDs.  I ordered the SuperBrightLED resistors from the link above.  I mounted them on the composite walls near the headlights.  Concerned over heating, I offset the resistors with leftover washers (as heat sinks) and nylon spacers.  I could have used metal bolt nuts instead of nylon spacers, but I just do not believe it will get hot enough to melt them.
Resistor wiring:
Both of the turn signals were fed by similar wires, blue wire with white stripe.  Resistors normally work the same in either direction.  For one lead of the resistor, I used the connector that came with the resistor.   That way I did not have to cut the blue/white wire.  It was hard to get the connector to cut through the insulation around the wire, but keep trying. 
I did NOT identify the ground wire, but rather I loosened a nearby bolt/screw and wrapped the “ground” side under the bolt and re-tightened.
  
See next post for pics.