is it all worth it?

I think that if you have the means and the car has some value to begin with then the answer is yes. Currently I am doing all of the sheet metal work on a 73 dart sport 340 4 speed car for a friend. The only option the car had is power brakes. It is very rusty, but the car has some value, so to the owner it's worth saving. It is a ton of work, but he will have a very solid cool car with some history.

My dart swinger actually started out as a very solid 73 model, but have added a 70-71 front clip on it. On paper the car has little value, but I also have no hesitations about changing it any way that I want.