In the sketch, the wheels on that Lincoln are way too big, in my opinion. They don't look as bad on the black car in the photo, again in my opinion. Yes, I do like "tuck and roll" to this day and may even do my dashpad in my truck with it, if I put the pad back in at all. I love the flake roof on the blue slab New Yorker that belongs to one of our members. He did a beautiful job on that whole car, AFAIC. The look "works".
That's one of the biggest problems. A lot of the time the look doesn't "work" and it ends up being hideous. I hate to diss somebody's project, but a case in point would be a local truck. I won't mention the make or year, other than to say it is a '50s era pick-up. The first time I saw it it was beautiful. It was painted a sharp looking color, the interior had been painted and reupholstered, the bed and tailgate had been customized and there was an early '70s modified V8 under the hood. It was a very cool little hot rod truck.
I didn't see the truck again for about ten years, when I happened to spot it at a cruise night. I walked over to look at it, but when I got to within about fifteen or twenty feet I realized something was terribly wrong. The first thing that I noticed was that the roof had been chopped, which isn't necessarily a bad thing, but in this case this truck didn't need it. The truck was perfect before. The next atrocity I noticed was that the entire original dash had been removed and replaced with a late model dash from a minivan or who knows what, but the damn dash was way too big for the interior. It just looked totally out of place. Then I looked under the hood and noticed a huge mess in what used to be a clean engine compartment. The early '70s brand correct V8 engine had been replaced with a late model fuel injected, computerized V8 of unknown manufacture. Almost all sheetmetal forward of the windshield had been customized and in no way could be called an improvement. I walked away saddened and muttering to myself about how they had completely ruined a nice old truck.
Like Stan mentioned, I have seen so many wagons, four door sedans and even two door cars have their roof hacked off in an attempt to make an El Camino/Ranchero and either end up never being finished and just hauled away as scrap, or they eventually are finished, but end up looking like hell with angle iron for bed rails and cut up culvert pipe for wheel tubs in the box (bed). There was one guy here that did do a really nice job on a late '90s Grand Marquis, which he named "Grandchero". He must have been an expert bodyman because it was actually very nice, but it was also the rare exception.
So, I can understand the viewpoint of those who say "leave it alone". As far as it being worth more, that may depend on the make/type of car, but at least it won't be rendered useless by somebody who doesn't have a clue. Sadly, it doesn't look like our C-bodies are ever going to be worth much more. They may go up a little, though. One of my buddies is a Chevy guy and we were talking about this, leaving it stock vs customizing it. He has a '57 and has also owned Chevelles and El Caminos over the years. His point of view is that you can do whatever you want to the engine, just don't alter the body. I more or less agree. Some people can look at a car and envision tasteful mods that work, others can't and once they start modifying don't know where to stop.