I applaud you for working to save an unusual and very cool Challenger from the ravages of the tin worm!
I have a N code JH car also, my convertible. And it is the same color too! When I was looking for a convertible 20 years ago, I wanted a solid turn key quality 318 car I could dress up with a twin scoop hood and rally or magnum 500 wheels for a nice local driver.
I was having trouble finding a good car, but a guy with a 383 car answered a wanted ad I had placed. It was more than I wanted to spend, and after I decided to buy the car despite it being over my budget, I still planned to get a "raisin bran" hood for it some day when my finances recovered. But I never did that, and I'm glad I didn't as I really like having a Challenger that is different than the rest of the R/Ts and clones at local shows and cruises.
Mine is an automatic and if I could change one thing about it, I would probably have it a 4 speed instead. 4 speed JH23N and JH27N cars are rare indeed.
Good luck with the restoration!