71 Dodge Dart Swinger Survivor the Real Deal

I agree, keep it original. Yeah, it's a /6, yeah, it's got a butter colored interior (IMO the worst color ever) but I still think you have a kick *** car. Since it isn't 100%, I would spend my energy making it as close to 100% as possible. Lose the radiator flush by replacing the heater hose, replace the hose clamps with the correct ones, replace the radiator cap. Lose the extra carpet and stuff in the trunk and do your best to find five of the original tires. They will be bias ply. That would make the car you have even more special in my opinion and not hurt a thing. There are probably other things under the hood that I didn't see that could easily be fixed as well. Typically, the prime "survivor" examples of cars are the more common, lo-po /6 and 318 cars. For this reason you might be surprised how easy it is (and cheap) to attain some of your needed parts.
I had this exact same car 20 years ago. Mine was a rusty pig and I parted it out. The only thing mine had that I don't see on yours is the factory trash/Kleenex holder that was held to the trans hump by a stiff wire that poked through the carpet. The box thingy slid down over the wire to hold it in place.