I actually just sodered the leds with resistor to the back on the gauges, it had to have been the easiest thing i ever did. Looks great for cheap
If anyone wants pictures of where to soder let me know. Not sure with post-98 gauges, might be different. I just wired up a led and tested the 2 metal spots where the bulb goes. Find out which is positive and negative, then soder.
Peace
MAtt