Pics and details below of my version of a boost gauge install. i know, i know, digital meters aren't the best choice. i prefer a mechanical gauge but i just couldn't figure out a place to put one that i was happy with.
regardless of the above, i'm pretty happy with the way this turned out. I bought a China made boost gauge off of eBay - i think a New Dragon gauge. i bench tested it against a high quality gauge i have and it reads very nearly the same. Now that i know this works, i can put a higher quality gauge in if this one breaks.
Taking apart the mirror was easier than i thought. a slim bone tool to pry off the back from the front cover and everything came apart. Taking the boost gauge apart was easier since i didn't care about damaging the case.
Once i saw the size of the LED's on the gauge, i could measure and tape off the respective area on the back of the mirror to locate them to.
the reflective etching on the back of the mirror is pretty easy to remove. i taped off a rectangle and patiently scraped it off with a sharp xacto.
next, i had to remove the LED's from the PCB and wire them to their original connections so everything could fit inside the mirror casing.
Mounting the LED's to the mirror was the hardest part. i cut a small piece of the gauge lens and used double stick tape to fasten it to the mirror. i used two 2-56 bolts through the LED mount PCB and screwed it to the gauge lens. i thought of using RTV to attach the LED to the mirror but i didn't have any.
When i was ready to put everything back together, i put some foam around the PCB to secure it within the mirror housing.
then drilled a hole in the back mirror housing to feed the wire through.
snapped everything back together again.
From this point, it was simply a matter of wiring a typical digital gauge. i ran the wire up over the headliner and down the pillar and went through the same location to get to the engine bay that IPD details for their gauge install. I picked up switched power from the cigarette lighter at the radio.
I could take this a step further and find a set of LED's that are green/yellow to match the dash lighting but i like the blue digits in the mirror!
Let me know what you all think.