If I am following along correctly, the guy has owned this car since the late 60s, and is staring his own mortality in the face.
I really cannot blame him for doing things on his own terms. What we get in experiences out of this one-and-only life matter more than all the Hemis in the world.
The man has a long term connection with the car, and wants to do something extraordinary in his life before passing on to who knows where.
If that is most important to him, who am I to condemn him? Yes, he could go out and find a 318 car and make the mods. However, it just would not be the same (again, he has a bond/relationship/connection...stop laughing! We all do this!) to that particular car.
To get a little more insight on this, rent "Love The Beast." Any car lover should sit down and watch it, particularly with the other half. My wife and I watched it a few weeks ago, and she came away with a much bigger appreciation of my love of cars.