Re: .308 Build infor.
IRA is a good company and has an excellent reputation for producing high quality products. Several folks here (and elsewhere) have used IRA matched receiver sets and individual lowers for builds with good success.
It goes without saying...BUT, just make sure if you order an upper from them that you get the correct model as they are one of the few companies supporting both the AR-10 and LR-308 platforms at this time. You'll also need to get in touch with them to determine availability of Armalite-pattern receivers at this time.