to sell or keep

I think you should sell it.
If you are even asking this question, that means you'll never be happy with the car.
If you really loved it and wanted to keep it, you would be willing to carry the project through regardless of the time and money spent to get it to where you want it to ultimately be.
Sell it and look for a car that you would like more than this one and carry it through until completion.
In my past i've sold off a lot of cool cars that just didn't ''do it'' for me.