It's called "theft by deception" and I've had to get the police involved in a situation of mine in the past. They took care of it with a phone call after I spent months fighting with the clown. You need documentation, dates, specifics and proof of conversations and promises, not just "he said, she said". I was lucky, many law enforcement agencies won't get involved without a person being flat out caught red handed, as I've also found out. I would talk to the local LE out there. Don't be surprised if they aren't interested in your problem. Attorney General consumer affairs is another option.

Most of these chassis shops, engine shops, parts places, etc. are not large corporations. They are not going to finance your project for you, and they have to protect themselves from the a-holes who want an engine or car built but only have $10 in their pocket. Who is able to have thousands of dollars tied up in a building full of custom stuff that some clown couldn't pay for. That's not have it's done these days. If you want something done on a COD basis and it's custom or more than a few hundred dollars, good luck. Too many flakes out there. I won't do it and I don't expect it to be done for me.

Do your research and pay attention. Get receipts. Use email and don't delete them. And if something sounds hinky, it probably is. If you're the kind of person who regularly gets fooled by Nigerian princes, you should probably get someone to help you with this stuff.