I saw what looked like a great deal on German-market AC-Unity AK magazines - made in Bosnia and Herzegovina - $5 a mag - https://www.robertrtg.com/store/pc/20-PACK-GERMAN-MARKET-AC-AK47-30RD-MAGS-UNDER-5-EACH-14p8950.htm - they look like decent mags, but they won't lock in to my AMD-65 - I can sell them without any problems, but I'm wondering if anyone else bought these and how ya had to modify them to fit an AMD-65?

What is the problem with fitting your rifle?  Only thing different with an AMD-65 is the front grip makes full size mags hard to rock in, which is why Hungary issued shorter 20 rd mags.  

And AC Unity mags seem kind of long for their capacity.  So that could be it.  

Besides that, it is likely just a bit needing to be filed or sanded off of some point or another.  They should fit any in spec AK.

Pretty typical that you may need to fit the locking lug on the magazine to the latch. Other than that, sometimes the mag sides are a little wide if your rifle has a tight mag well. Plastic mags will eventually break in, or you can sand the sides of the mag where they go into the mag well. I have a lot of AC-Unity mags in 7.62, 5.56 and 5.45. They are good range mags. Probably just need to file a bit of off the bottom of the locking lug on the mag.