For the guys or gals crazy enough to want a big, slow, loud and hard to drive MV to restore/play with, here are some thoughts on getting into your first CCKW.
First and foremost, DO YOU HAVE A PLACE TO PUT IT? You can sneak a 353 into and 8x8 garage door, but you will be doing a some prep work (lowering everything) and will only have inches (or less) to spare. A winch truck is just shy of 20ft long. So after you drive it in, will the door close? I currently have a 24x40ft garage with a 10x10 door and the CCKW takes up its fair share. Working on the truck in that size garage is OK, but other vehicles still need to be moved depending on what is to be done. I would advise against outside storage (unless your climate allows) because things like canvas will fade and deteriorate, bird droppings, rain etc will take a toll on the vehicles paint and tires.
After you have a place for it, what type of truck? Do you want to restore a truck or get one done? I've looked at a quite a few trucks and there are significant variations in the term 'restored'. To some, painting over the rust is a restoration. To others, disassembling every nut and bolt, sandblasting and repainting every part, repairing and replacing with NOS or take off as needed is a more proper definition of 'restored'. The completeness of your truck will dictate the price. My guide is as follows:
Parts truck: No more than $800 for a chassis/drive train. No more than $2k for a truck with a bed. These would be trucks with most of the parts in place (hood, fenders, drive shafts, wheels, good cab sheet metal, engine with all accessories).
Work truck: No more than $5k. This is a driving truck with breaks and all the major parts: cargo bed, cab and seats, running engine, and a winch. Take off about $500-$1000 if no winch. Most of these trucks were put into running condition by the owner (or previous) and generally do not have the factory parts, so while they run, they generally do not have the original parts to justify more money. If they do have some of the hard to get or commonly missing parts (proper gas tank and fuel system, proper electrical, spare tire carrier, bed with tailgate, etc) then add more, but generally the condition of these parts will require some work, so do not overvalue the truck just because it has a spare tire carrier, it may not have the correct spare tire lugs, or other issues that will be hard or to expensive to correct).
Motor Pool Truck: I borrowed this from the jeep guys. This is what I would call a mostly correct truck (drivetrain, cab, bed, accessories) but not in a restored condition. It may need paint or reconditioning (NOT repair or replacement) and will drive, stop, turn etc. All that would be needed is a good repaint and you have a truck right out of WWII. I value these trucks between $5k (353 cargo w/o winch), $7k (cargo w/w or dumper w/o winch) up to about $8-9k for a dumper w/w.
Factory Trucks: These are the show girls. All parts are correct, painted properly and installed correctly. These are the $15k+ trucks that get on the covers of magazines.
Be warned that working on a CCKW involves some truck sized tools that you almost certainly do not have. A complete set of 1/2inch and 3/4inch sockets may be required for some drive line work... as well as the standard tools. The GMC 270 engine is a HUGE beast that weights over 500lbs in full gear. Working on the truck can be amazingly easy, with the right tools. An air compressor with an impact gun is a must.
Parts for a CCKWs are available. There are a few vendors, but most of the CCKW owners trade among themselves. E-bay does have some parts, but bidding can quickly overinflate the price of an item. Rare parts are just that. There are very few reproduction CCKW parts, and as with most reproduction parts they are not 100% copies. The technology used in the mass production of parts (stampings, forgings) do not scale down well. NOS sheet metal is scarce, most sheet metal is take off. Engine parts are available as the GMC 270 was in production till the mid 60's, and many civilian trucks used it. The only parts problems are related to the brakes. The original hydrovacs used on early and mid CCKWs have long been discontinued. Rebuilding of original hydrovacs is an option, but rebuild kits are $500+. Mater and slave cylinders can be resleeved, but most times good rebuilt ones are available. Drive shafts, pillow blocks, axles etc are all available as take off.
The CCKW is lucky in that it has two close relatives... the 1.5 Ton Chevy and the DUKW. If you are looking for a part, it may be available from a person/truck/vendor that deals in those vehicles. Brake parts, some sheet metal etc will interchange, ask around if you are not sure.