Classics has M77 stock converter to convert slant back M77 to accept AR stock. Appears to be an item that they make themselves. $40 is kind of high but not too bad.

https://www.classicfirearms.com/m77-stock-adapter-aluminum-for-ar-15-stock?utm_source=Classic+Firearms&utm_campaign=a2aa6f3a9e-Mailchimp_2015-04-10_M77&utm_medium=email&utm_term=0_afe48e03d8-a2aa6f3a9e-239384045

I made a stock conversion from molding laminated epoxy in a mold made of cardboards! The side folding hinge is a modified UTG AK side folding stock adapter (TL-K7FAD01) by removing the male side threaded stud. Mag is a converted aftermarket  M14 mag. The muzzle brake is a modified TAPCO AK74 brake.
M14 mag is bit too long, so most conversions by cutting a front key slot, I don't like the look and squash the mag at the front a bit, doesn't take much, and silver solder a locking tab.







http://leapers.com/prod_detail.php?mitem=Accessories%20and%20Parts&itemno=TL-K7FAD01
eBay price is much cheaper!