Interesting project. Looks good.
A couple thoughts come to mind.
One issue you may already ahve thought of.... those inks need to be UV stable. Allot of regular inkjet ink and laser toner isn't. You don't want to put in all that work and have it fade in 6 months or less.
In order to get the gauge brightness right,,, you may have to play with the dash bulbs or the dimmer.
You may have to split the gauge lights off from the main dimmer transistor and add second one and play with some resistors.
If you go that route you'll need another dimmer transistor and wire harness connetor. Those are easy to get from any number of GM cars.
You then would connect it sort of parrallel to the original one. I say sort of because you'll need and adjustable resistor between the wire from the dimmer knob and the "base" terminal of the transistor.
You could also see about using white LED's instead of bulbs. The LED's could be positioned to reduce shadows from the gauge equipement on the gauge faces. It's a good amount of work but it would potentially provide more even light and eliminate lamp changes. (White LED's will outlast the car.)
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11-Sept-01, The day the world as we knew it ended.