how much is the adapter?

I wonder... would it be possible to sell the adapter kits on eBay (which seems to get a lot of slant six traffic) with a future ship date, using a "Buy it Now" only sale?

That would perhaps sort out the "lookers" from the "spenders", give you some seed money, and give you a firm number of kits to build in a batch (maybe with two or three "runs" a year).

Another option would be to prepare and provide the specifications for the adapters. I'm not sure what format that would take - a writeup, some drawings, perhaps CNC files?
The information could be sold online, mailorder, etc. That would give you some compensation for the time and effort of figuring it all out, and allow those who are willing to work at it the benefit of your knowledge.
Of course, once a machine shop has them, they could make as many copies as they wanted - not so good for you, should you eventually decide to make them again.
Just thinking out loud.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO