I hear you on the 20/20 rear view. All I'm saying is on almost any of these projects, replacing the interior is a given, glass can be saved most of the time, or can be found relatively easy, motor/trani again pretty easy.
Ok so now the meat of the argument the sheet metal:So if a car has poor sheet metal, One guy may say "junk the car", another may say just replace enough to get it on the road, ( I have a friend who just fixes the metal enough to make them a 20 ft road worthy car), another may go front to back giving it necessary sheet metal. It just depends on the guy, and his initial investment in the car.
But I will tell you this if you have a good roof and firewall, and vin, you throw some full quarters on it, and it may seem like your half way done at that point and over the hump.
I have another friend that bought a plain jane 65 mustang coupe. (original v8 car). And replaced A LOT of metal on that car, we both learned to mig weld on that car. He basically saved it from the junk yard, because he liked that body style and got a deal on the rolling chassis.
The right buyer has a dream of what it will look like done, and sometimes it is the journey of bringing the car back that is worth more than the first drive when you get it done
(1964 C/10- the only original metal on the this truck is the radiator support and frame. 7 or 8 rusty long beds and 1 short bed gave their life so my truck could see the road rust free)