Hey Prowler,
I can understand your frustration. I'm with you, I hate loosing money on anything too. $15K for a '71 Challenger with a 383, regardless if it was 318 before, isn't a bad deal considering what they're going for today. Dude! It's a '71! I would love to have a '71!
Don't give up hope yet. Don't get rid of it, don't part it out, unless you're really hurting for money. I know what it's like to be a little low in the cash flow. I haven't been working for a while due to medical reasons and the thought of selling my Challenger crossed my mind but if this is the car you really love, don't give it up. You're already are familiar with this car. It's not like a basket case. Think about how much it'll cost to buy what you already have now.
Definately what the previous owners did by misrepresenting the car was WRONG. But I don't know if there is anything that can be done now. If life gives you lemons, make lemonade. Just work with it for now.
If that paint guy hasn't got back to you after 3 times, I would find someone else. That shows his integrity and character.
If money is a concern, it doesn't have to be a show winner. I think once you get it up and running, work out the bugs, and drive it a bit, your feelings of frustration will be taken over by feelings of joy. Your paint looks decent (better than mine!!!) from the pics I've seen. You just got some sweet tires and rims. If you don't have the $$$ to make it really sharp looking right now, do it later, get the car together and save you nickles and dimes for another day when the $$$ situation is a bit more optimistic.
I would love to have a car to drive and win some shows but right now that isn't going to happen for me. I do things on the cheap side to make it presentable. I don't buy new door panels, I refinish the original panels, sand down the wierd surfaces. I don't buy $25/can Mopaint, I get $4.99/can Plasticote interior paint. (Actually matches exactly the blue interior!), I bought used R/T chrome tips instead of new. You get the message..... I'm not saying that's what you should do, but just to give you some ideas...
I just hope you hang in and keep your car. You may regret it later on if you sell it. Hope all works out for you!