When I started on my dash project I had a brief moment where I considered trying to package and sell dashes, kits, individual parts, etc. The conclusion I came to is that the market for something so specific is too small to get the cost down to something people would accept.
At the time there was a company called ID4Motion making retrofit cluster for various older BMW's, probably a larger market than 86+ 240s, selling plug and play dashes for ~$800-1000 that were pretty well executed, especially compared to what I was making. Most of their social media feedback was complaining about how expensive it was. If people weren't willing to pay that for a complete product, it was unlikely that I was going to be able to sell kits at that price, and a fully tested, commercial product that I would feel comfortable selling to people would have been way more than that. It looks like they've completely scrubbed their website/social media footprint, but here is one of their
indiegogos and someone did some reverse engineering on one of their dashes
here. Standard stuff for low(er) cost application processor based designs with a SODIMM SBC module with a secondary processor that likely handles the CAN and ADC.
Either way, if there's anyway I can help you get things off the ground, let me know.