It's very rare to find original AR-10 parts kits anymore.
Not impossible, but probably harder to find than the US compliant rifles that were made on the imported barreled uppers and US made lowers in the eighties.
Print information from various sources: Maj Sam Pikula, Blake/Ezells Black Rifle book, etc. seem to agree that aside from about 50 original AR-10s made in Hollywood, CA. about 1956-57, Artillerie Inrichtigen made almost 10,000 of them under license in Holland before production completely stopped sometime in 1961.
Of that number, many imported to Australia were destroyed as a result of the drastic change in firearms ownership laws there. Maj. Pikula estimated 1500-2500 were destroyed just in Australia, which had a market for them as cheap 308 rifles, either select fire or with the auto sears removed, about 30-40 years ago. And most of the AR-10s used in Africa by the Portuguese commandos, and most used in South America by a few countries, are gone.
Probably less than 5,000 original AR-10s are left in the world. Of that number, some are the kit rifles that we were discusing.
Some of the kit rifles were culled from left over parts at the factory bought up and sold by the European company SIDEM.
So there are very few of these great old rifles around. They are few and far between.
If somebody has seen an original AR-10 kit for sale on Gunbroker and they don't want it for themselves, please contact me by instant message or by my email, which can be found in my membership profile. I would probably be interested in buying it.