Read this. There are 3 pages.
http://www.m1carbinesinc.com/carbine_natord.html
Some parts are not even close to issue part dimensions. The early receivers were built on scrapped(Right out of the scrap yard. Some were unfinished with bad heat treating.) issue receivers or cast. Barrels were made by casting the gas parts and some by cobbling together scrapped issue barrels. Or used surplused 1903/1903A3 barrels with the gas system welded on.
There's one on Gunbroker with a starting bid of $589.00 that has no bids. $600ish is decidedly optimistic. Kind of suspect Lyman's $450 is too.
Spelling and grammar count!