Man I must be a boomer based on some of the comments here.
I think old cars (any old cars) are cool, regardless of it's a I6 and 4 wheel drum. These cars are sought after for their styling and in other cases the nostalgia. I'm a nut for history too so that does play into my personal viewpoints. If those cars didn't exist we wouldn't have 400+hp cars getting 20-25mpg today.
I'm doing a restomod but I'm doing it only for the styling and not really the nostalgia. I personally think (and I know a lot of you will disagree here) that the majority of older cars look 1000x's better than some of the plastic junk rolling around on the streets today. Let me take a minute to expand upon that. My 3rd gen nova was classified as a compact, economy/budget car. Take how that looks and compare it to any cars made in the last few years in the same category. To me that nova is a lot sexier, granted a camry would have blown it's doors off in every aspect. That's why a restomod fixes the technology gap of a 50 year old car and looks a whole hell of lot better.
Granted there are some sexy sports cars out there now and I do like a good number of them. But if I am going to drop 50k+ on a car it better tick every fricken box of what I want. Otherwise I'll do what I am doing now and build my own for less.
I think a restomod done right can be really cool, but the modern cars will almost always out perform it, in nearly every measureable category. Looks are subjective, yeah I think some of the old muscle cars are really awesome, but I think there were quite a few duds too. I guess the big question is what are you going to do with the car? If it's just a cool cruiser, that you won't take on appreciable distances, a non-restomod would be fine. Anything over a couple hours in the car or ANY track duty (auto-x, drag strip, road course), I'd probably start digging into suspension and a cage at the very least.
But honestly, I don't know enough about carbs to be able to properly tune one, and the same goes with a distributor, so as heinous as it sounds, an LS swap (even a base iron block truck swap) is preferable. It'll almost assuredly have more power, torque, and efficiency than whatever motor is being taken out, the computer figures out all the BS, and it should just run. Slap a sloppy cam at it to make it burble and some valve springs, and call it a day.