Reese Surplus used to sell complete kits less the receiver and selector parts for $400 and you had your choice of matching parts by SA, Win, HRA, and TRW.

Their ads were in the Shotgun News issues throughout the 90's. Back then no one had any use for the parts though as no one (that I know of) was manf semi receivers.

When Springfield Inc began business their early M1A guns were made of the surplus parts (less receiver) till they became more scarce and costly.