BUT WOW, that is impressive! Completely custom install. Very very cool.
i think what you might be able to do is forget trying to display via the mirror like that. Leave the V1 mounted in the rear, take out the LEDS and such, and tap the wires are connected to the arrow leds and run them into a carputer, decoding the "number" part should also be pretty easy and basically have the carputer up front display all that.
i think you have a carputer right? you were making bezels awhile ago?