This is not for the faint of heart, but I thought I'd share the info just in case. I had found the perfect voltmeter some time back, but when the 3rd one died after getting wet, it was time to get a more reliable unit. Got one from
http://www.digitalmeter.com Got the $6 bezel with it, cause I wasn't sure where it was going to end up on the bike and figured if I wound up putting it where most folks do, then I'd need the bezel. I really wanted the meter up high, or near the gauges, but couldn't think of a clean installation of it, unless it went inside the cluster. The only question was, is there room for it? When I got the '01 from Mike in IL, I had to take the cluster out to fix the tripmeter. While I had it out, I looked to see if there was space behind the tach, and there was. I didn't have the meter yet, so I wasn't sure if it would fit for sure or not, and I wasn't ready to leave the bike torn apart until I could spring for the meter, so back together it went. Couple months went by, and I've got the meter, and I'm ready to install it, but don't know where yet. I got a junk cluster from Carl to experiment with, and the experiment went well enough, that Rick near Kansas City wanted his meter in the same spot. Here are the gruesome details, LOL.
Once you have the cluster out of the dash, unscrew the trip meter knob, then the 6 screws holding the lens on.
Carefully lift the lens off the cluster.
I recommend wearing gloves, or covering the entire cluster face with something like blue painters tape, if you have oily hands like I do. I didn't cover it, and I have greasy residue now on the outside edges of the cluster face. The matte black just doesn't look the same once it's been oiled up. Live and learn.
This is the area where you'll be cutting up.
Do some checking to see where the meter would best fit.
Once you're satisfied with the location, and you understand the gravity of cutting into a 10,000 mile cluster from an '03 Voyager, very carefully, scribe the outline of the meter.
Once you have the outline of the meter housing, and since there's already no turning back, it's time to start cutting. I had the best luck using the following method. Carefully drill a bunch of small holes as close together as you can get, all the way around the inside of the scribe line. Then take a small dremel cutoff wheel, and cut the plastic between all the holes. You'll have to cut on both sides of the face, since there are two pieces of plastic and you'll have to do it a couple times, since the plastic has a tendancy to melt and move around, instead of being removed.

"You only live twice, or so it seems. One life for yourself and one for your dreams...." Nancy Sinatra
"If a man made it, a man can fix it." - Steve in Sunny Fla