Am I crazy for doing this on a 65 Barracuda ?

And when/if you repair it again you might feel that way. Some people can't see other methods as ever having merit.
As a former fabricator I'll bend a piece for lower rockers around a piece of pipe the right size, and then wheel it, if needed, since I have no brake now. WW lips are more difficult , but I have shrinker/ stretcher and will get there.
Door bottom repair panels and others are available w/prebent lip from millsupply.com. Also small partial sheets and also notched lip repairs that aren't a very good repair. But they sell to bodyshops all the time, so all bad repairs can't be foisted off on newbs, as many know when they do poor work & aren't proud enough at what they do to take the time.
Enjoy your Barracuda!

I tried to emphasize the importance of treating and sealing the areas to keep the damage from reoccurring. The factory didn't always protect these areas as well as they could have and people never paid attention till something showed up.
Any failed bondo job you see is probably not treated properly. There are probably a lot of sheet metal replacements not treated properly also.
If a person treats and seals and lets an area vent where needed I don't think they will have a problem regardless of which method they used to repair.