Like most all build vs. buy questions, the answer depends on these things:
1. Do you enjoy building cars?
2. Is the concept more important to you than the money?
3. Do you want to enjoy the end product now, or is the journey to get there part of your enjoyment?
4. Will you actually explore the limits 100% at the track, or is it a street car?

It's almost always less expensive to buy a finished project, like the '71 B mentioned, IF it's done right and it's to your taste. You need to set the goals & budget. I can appreciate the new stuff, but to me old cars are WAY cooler and usually a better investment. I've built enough cars to feel confident that I can do an early Camaro, Mustang, Challenger, etc that would equal the new models' performance for about the same money.