You have to be rel careful with gunshop Garands. Many of the ones I've seen at gun shows and shops have worn barrels.
The vast majority of Garands will have receivers dating from WWII as that's when most of them were made. But the barrel has often been replaced, and because none of the other parts are serial #'d, they may be later replacements.
A WWII stock will have a proofmark and stamp from one of the military inspectors. Postwar rebuilds will often have a replacement stock with a "Defense Acceptance Stamp." Because the wood compresses, cracks, absorbs oil or has other problems, they have often been replaced. Unfortunately, fake cartouche stamps are readily available and some Garands have counterfeit stocks. A rare WWII stock in good condition can sell for over $300.
CMP has started selling CMP rifles with commercial replacement stocks that are GI pattern and look the part. Stock fitment affects Garand accuracy so that's important. Good way to keep these rifles shooting and eligible for JC Garand matches.
Another accuracy issue connected to the stock is lock up. The removable trigger assembly has pins that clamp it into place. If these pins are worn, the stock won't lock down tight. These are easily and relatively cheaply replaced.
When WWII barrels were more available, I used to buy Rack Grade rifles and rebarrel them with a period correct barrel, fix any problems, and resell them as shooters. Now that those barrels are rare over $200, it's not worth it anymore. While folks worry about chamber erosion, in my experience having a tight muzzle is much more important. As a rough guide, a Lake City bullet will show at least 1/8" band above the cartridge neck. If it is closer than that, accuracy (and value ) is affected.