I second the idea of making "parts" for airplanes instead. Make discrete aircraft instruments. You'll make a killing off of them. Even questionable used junk on ebay is through the roof. You could sell some of them into the automotive market as well.
Pound for pound, they probably sell for more than gold or latinum. If I started an aircraft parts cottage industry, that's what I'd do, like Belite. Only not with LED dots. Real numerical output...
Start with a glider / sailplane /ultralight airspeed indicator... 0-80mph/knots in one revolution. That would be the hardest to build. There's only one single one out there, and it sells for $340! (the one above) I can't afford that... I'm going to have to build my own using the guts of this. Just because I don't want to try and read a rain gauge 4 feet off to my left outside the prop wash.
Then flush our your line with even easier instruments to build based on repackaging chinese digital electronic parts. An altimeter Tach. Temp sensors. Most could be built with digital voltmeters ($1.35 a piece) or digital frequency counters ($9) for a readout. Sensor input voltage --> programmable cheap chip looks up input value in table, to output table value--> serial display. Some of the temp sensors are cheap on the car side, but expensive on the aircraft side.
I am so tempted... yeah they'd be little hokey devices, *but* they'd be lightweight, and cheap, for paraplanes, kit planes, experimentals, ultralights, gliders. Old GA instruments are huge and bulky. Sell them in bundle deals.