Well that sounds rather discouraging. You'd definitely need a new rear trunion, but getting a stock to fit on one of them angle cut receivers would be a pain. I guess you could always just weld the Ace mounting thing onto the gun?(unless its aluminum) Either way, you're bubbatizing the gun even further. Not necessarily a bad thing, but you gotta figure if it's worth your trouble.
If you do decide to get one of the MAADIs, make sure you can return it if you get a stinker. (unless you feel like working on it) Rack the slide, and make sure it has a slick action and doesn't bind on the hammer, or receiver rails, then check the sights for straightness. (check bore for a live round first!

) Throw away the nasty sand and paint encrusted 5 rounder it comes with. (I needed a mallet to remove mine)
When I bought my MAADI, (Century, not Steyr) I knew nothing about AKs. Unknown to me, my particualr specimen was a total piece of junk. Front sight base was WAY off, gas block canted slightly, cleaning rod bent, gas piston bent, rear sight ladder adjustment rusted in place, hammer not even close to being in spec, receiver pinched in the middle which restricted bolt movement, and the finish looked like someone dumped dirt on the paint while it was still wet. Amazingly, it STILL WORKED PERFECTLY, I just couldn't charge it very easily, or hit paper at 10 feet with it.
Thankfully the AK-47 was designed so even a chimpanzee with a big hammer could work on it. Rather than sending it back to the morons who messed it up in the first place, I took it upon myself to right their wrongs. About $50 worth of replacement parts, and a little elbow grease later, I have a fully functioning firearm. It has performed flawlessly ever since. I also kind of like the looks of the gun. A very good copy of the older Soviet AKs once refinished.