I think Tim said plenty there, but I would add this to the mix as well... Unless you have a truck that was customized in the 50s or 60s, and done really well, and is a good representation of that period, it is really tough to "hot rod" a truck or a car for that matter, and have it hold any value. A stock, or close to stock restoration, with some period correct non-stock upgrades, will always hold value, and stand a chance of appreciating with time better than a modernized version of a custom truck. 90% of the time, the truck is most appealing to the one that built it. If you want a wide market to be able to turn the truck with, go more stock. In the end it comes down to univeral appeal and having the largest audience that can appreciate the truck. GM sold a lot of those trucks, and so they must have done something right. First generation (1953 GMC, and 1954 Chevrolet) Hydra-Matics are very uncommon. Not only because of the relative newness of the option, but because the factory that produced those transmissions burned to the ground, and so the production was very limited. They became much more common to see in the 55-59 trucks. If you have a good functioning, relatively complete H-M, I think you'd be doing it a disservice to alter it much from stock. Just my opinion though.
http://www.autotran.us/TheGreatHydraMaticFire.html
