Yes, check M1Sniper post above for link to his information. Don't IM, send an e-mail, wait for reply. Patience is the key for retro good deals and the better condition parts (litle luck doesn't hurt either). In a hurry, expect to probably not get the best of deals, worse parts condition or fall to some serious salesmanshit at possibly it's finest this side of a used car lot.
Most quality vendors don't need to advertise, word of mouth is king. Expect waiting lists with these quality providers. NDS is the prime example for retro receivers. JT, Retro Arms Works for retro repair, Young Mfg for BCG's, barrels Compass Lake (not retro), White Oak (not retro etc.). They're the good guys with the best stuff, quality of craftsmanship, etc. These won't be the lowest priced but you generally get what you pay for. RRA for small parts (best service and decent pricing), are as close to true milspec as readily available without buying true milspec Colt or FN & couple exceptions not retro. RRA line of weapons is pretty good also from AR's to pistols but again not retro. JSE Surplus is top flight for the small business but some of their retro is same reproduction everyone else sells. Pick & choose, no internal cc fraud and great customer service.
I generally only use the true milspec parts from Colt & FN but Colt has dropped out for the time being, causing increase in pricing / availability and lots of used Bubba'd junk for inflated pricing. Centerfire M-16A1 kits are cheap enough right now but probably need a can of Sandstrom dry film lube to make look like much. Neither Colt or FN actually manufacture most all of their parts and never did but they do mfg the potential liability issue pieces with milspec quality control. The other pieces are actually purchased from sub contractors, springs from spring mfg's, bolt, screw and pins from bolt, screw & pin mfg's. This list goes on an on but there are better quality mfg's on these also. Lot of Chinese crap finds it's way into the mix unfortunately. Snap-On or Harbor Freight? Depends on the job / task at hand. I use Harbor Freight but I wouldn't confuse their wares with quality of craftsmanship either.
Most all the reproduction parts available today are low tier, maximized profit stuff. Reproduction / fake stuff always has been generally. It's our world on a regular day to day basis unfortunately. Under engineered, not over engineered. Don't expect your new refrigerator to last as long as the one it replaced, would be a fine example of this. Lifetime warranty from some vendors is great unless weapon kills you and voids the warranty to boot.
Keep in mind Covid-19 right now has slowed production / availability from the better places especially in states under Dem control. Numrich for old authentic retro furniture is a prime example. Closed for Covid-19. They will open back up. Lot of that authentic stuff does require some finesse and they will screw you also. Coin toss many times but they take returns. Generally not "sold as is" unless humper project stuff. Pics might not be actual item one receives. Sarco never returned anything in last 10 years that my dedicated cc didn't buy a bunch of cell phones within 20 miles of Easton, unfortunately for my financial institution and my wasted time / resources.
It's a buyer beware environment on the real stuff an always has been, always will be. Do homework before going to class. Better sellers will show all possible flaws they observe. Poopheads will hide behind I'm so great at this or that while ripping you off. Most sellers too busy tooting their own horn aren't worth the waste of time or resources. If you see wording in ads or advice like "I'm or I've" don't walk, run away. Cool isn't telling everyone how cool you are (Gov Coumo?), cool is when everyone else says it and no one gets damaged from association, whether jailed, physically injured, etc.
Dems are playing politics at the expense of their tax paying citizens in more cases than not, with promises of gold paved streets and the only gold paving is in their own driveways and such. Not all of them but waaaay toooo many none the less. Can't go to church but can buy some pot or get an abortion with no problems if that's what one desires. Pretty much shows where we're at politically and socially unfortunately the truth cuts rather deep especially on thin skin. I'd rather have the US Constitution & it's amendments with firearms and property protection, freedom of speech and religion than pot personally and most here probably feel the same unless part of our unfortunate uneducated brainwashed youth movement of last 20 years or so and really started with President Dwight D Eisenhower for recent times anyway. Few today could even tell you what the Douglas debates were about even with a PHD in American history.
DD is great stuff also. LMT, Wilson Combat, to name a few but there is a short list not a long list. Enjoy your Memorial Day and your freedom where ever possible. Please think of others who gave their lives for the flag, not yourselves. Dave's how to buy retro or quality AR parts guide! Quack! Quack!