We are fortunate with this era Dodge trucks. This is the cab/chassis most of the WW2 Dodge military trucks were built from. The military trucks have a huge following, so parts are still being reproduced by a few good companies.
www.vintagepowerwagons.com reproduces a lot of mechanical parts that work on our civilian trucks. www.robertsmotorparts.com also reproduces a lot of civilian truck parts, when your looking for new stuff, I go to each of them 1st. Being the reproduction people, almost everyone that offers parts from these trucks get them there, mark up the price and sell it to you. However, there are some smaller operations that also reproduce parts for these (and other Dodge trucks), these two are the major suppliers, but not the only suppliers.

A lot of the mechanical parts can still be bought new, maybe reproduction, but pretty accurate stuff, some with improvements built in to correct the original flaws.

Unfortunately, most body stuff (and nearly any other repoed part) is made on short runs, if you happen to be in the market as a run is going on, its your lucky day. After the production run ends, the parts become scarce (and pricey) until the next run is made. The only reproduction fenders I've seen are fibreglass, and also fall under the short run issues. Gene