You are correct it is Sudan. Some years ago both the Portuguese and Sudan kits were imported into the
USA
, being selective fire the lowers were missing or demiled. There were a
few small firms that built lowers for these kits, some were steel. Sendra made a lower that was selective fire. But most lowers were semi auto, all worked very well.
I understand that there were some variations to the Portuguese and Sudan rifles such as an aluminum butt stock for rifle grenade launching and some wood butt stocks as field replacements.
There may be some incomplete kits around but any parts are very difficult to find and everything is different from the AR-10 commercial rifles now manufactured