Stock vehicles sell for the highest amounts. You never see a modified Corvette sell for more than a low mile factory original.
Nor would a Cadillac collector what someones modified mess.
Honestly the reason a modified truck may go for a decent price is likely because no one really knows what an original is supposed to look like, I have never seen a factory stock restoration of a TF pickup no where. Mods are easy, factory stock is not, thus way more desirable.
I take issue with your comments Truckrolet.....if the vehicle is a " rare " one, then bone stock is the way to go. With common stuff such as most of our trucks, well done " restomods " or customs are selling for way more money than stock trucks. That being said, most of those customized trucks have had big $$ spent to get there, and likely the builders are taking a bath on the sale. I don't think you can go into this process with the idea of making money, either stock or modified. Do it for the fun / pleasure of the build, build it your way, and enjoy the results.