After only about a week, the boards were added to a "fab", printed and separated, and shipped.  Here they are, waiting for the components to be soldered on.

I'm leaning away from the "tachometer transplant" method based on interest in the project from others.  I'm currently considering strongly a custom-printed or -fabricated enclosure that mounts behind the steering wheel to the fixed portion of the steering column.

It should be easier to wire to, it would provide a housing for the four buttons I am planning for menu navigation, and it would not block anything except the "Unleaded Fuel Only" sticker, which for my car is slightly off-center which drives me nuts anyway.

For making the enclosures, I'm currently considering the gMax 3D printer - it's the only one large enough to print something bigger than cufflinks, so it would be useful to me post-project. Something like a 16x16x9 inch print area. My intention would be to figure out how to print A-pillar covers afterwards...

Currently working on proof-of-concept enclosures in TinkerCAD.

The components for the power supply are on order from Mouser, so it's time to send the printed circuit boards out for manufacture.

OSH Park will be handling this first batch.  I like their online configuration system and it takes the Gerber files out of Fritzing with apparently no problems.  It's also cheaper than Fritzing's built-in manufacturer, which I suspect is EUR-based as well (prices are in Euros).

And, they're an interesting color as well (purple).

[Pictures removed, due to design being deprecated.]