Garands were made by 6 different entities;Springfield Armory(the majority),Winchester,International Harvester,Harrington & Richardson,Beretta,and Breda.A good number of components are marked with drawing numbers and revisions thereto as well as manufacturer's identifiers.
Most Garands were overhauled/re-built in service at least once,if not several times.All components are interchangable regardless of manufacturer.When rifles were rebuilt parts were simply replaced without regard to manufacturer(or to the sensitivities of collectors 50 yrs downstream).Stocks and barrels were replaced with great frequency,so it is next to impossible to find a sound and original stock or barrel on a WW2 Garand-although I have a 1942 Springfield Raritan Arsenal re-build with original barrel which gauges near new.
Your best reference on the WW2 Springfields and Winchesters is the Scott Duff red book which lists and illustrates parts and the timeframes where various revision numbers were used in manufacture.Duff's blue book on the post-war Garands is helpful,but badly out of date. The good news is that a lot of the Springfield,IHC,and HRA components show the manufacturer's identifier in connection with the drawing number. The Beretta and Breda rifle's components are quite liberally marked with the makers identifiers(PB for Beretta and BMR or BMB for Breda).
As stated,original matching Garands are a rare bird indeed.If you have the time and money most components can be located to restore a Garand to it's original "matching" parts configuration.Be advised that original stocks and barrels are very tough to find for the WW2 Garands.
