Has this been perfected yet? Would like to build something to share ammo with my AK74.  Even thought about a 7.62 upper since I don't shoot the SKS much anymore.

These came up in a search,

{Olympic Arms 5.45 AR-15 Upper - $549.95 : Military Gun Suppl...
Military Gun Supply Olympic Arms 5.45 AR-15 Upper - New from Olympic Arms! 5.45 Upper to fit any standard any AR-15 Lower. These uppers are in a flat-top ...

www.militarygunsupply.com/shop2/index.php?main_p...

http://www.militarygunsupply.com/shop2/index.php?main_page=product_info&products_id=461

Smith & Wesson M&P 5.45x39 AR-15 Upper - $579.95 :...
Military Gun Supply Smith & Wesson M&P 5.45x39 AR-15 Upper - Smith & Wesson M&P 5.45x39 AR-15 Upper. These uppers are desgined to work with any standard ...

www.militarygunsupply.com/shop2/index.php... - }

There are many others making the 7.62-39.

Hope this helps you.

Best,

yls