The good news is that there are thousands of well-preserved Pagodas out there. There are plenty to satisfy even the most persnickety of Concours judges. I admire owners like Mike Salemi, and Bob Possel who have gone to such great lengths and expense to restore their cars to such a beautiful state. I also admire the originality of the mechanical fuel injection and the torquey little straight 6 engine. So I know there will always be plenty of examples of originality to see whenever I like.
However, it is the body style and the pagoda roof that are the real attractions. So, if you can have the style of our great cars, and the better performance from a newer, more powerful engine, why not? It's your car, make it yours! I am much happier with my car since I installed a 5-speed transmission. I am happier because I have experimented with my springs and found the combination that is right for me. I am making other mods that don't change the outward appearance but make my driving experience better. I rebuilt my engine myself in my own garage for the experience of it. If someday I decide to replace it with a fuel efficient, high performance V-8, I won't hesitate do that. As long as the change makes the owner happy, he should do it.
If a car can be pulled out of a river and restored, I'm not worried that a modified car can be returned to standard.