There is no such thing as "numbers matching", as is commonly referred to, on these trucks, due to the wide range of years, their parts interchanged. Unlike the vintage classic Corvettes, Chevelles, Mustangs, Cobras, and the various MOPAR offerings.
It is possible to pull a casting number from any part, that has a readable casting number on it, from one of these trucks ('46-'72) and discover that said part was available, as standard equipment, on several years & models. The truck could have a part on it, that was produced & installed 10 years after the truck rolled of the production line.
Conceptually speaking, numbers matching, is determined when the VIN tag or other criteria connected to the vehicle, identifies the equipment the vehicle was equipped with, at the time of production. As with the Chevy trucks of this era, the VIN or GVW tags, did not identify the R.P.O.'s of the vehicle, therefore it is virtually impossible to determine what equipment was on the vehicle without some supplemental documentation, like an SPID label, original build sheet, dealer invoice or customer order form.
Here is an excerpt from an informative site, regarding the cliche "numbers matching":
Depending on whom you talk to, the definition of a “matching numbers” car may vary. A classic car purist might say that a truly original, matching numbers car will still have all the parts that it was manufactured with, including the tiniest nut and bolt. That would be very hard to find in an older car, so a more practical definition might be that all the parts will be either from the assembly line at the time of production or have been replaced with authentic NOS (new old stock) parts.
The most general use of the term “matching numbers” would mean that the engine and transmission are marked with the same sequence number as the chassis VIN number, and the rear axle/differential’s date code and casting number corresponds with the vehicle that's being checked.
Numbers matching 
