Or FAL?   I know with the M14 you would have to rivet a plat with a tongue on it to engage the front of the magazine, but how different are the rear latch lug heights?

The FAL appears to be similar to an AK style in latching, but I think the rear lug has to be built outward more.

It seems like a worthwhile concept, AK reliabilty, M14 power AND capacity.

I have not done the conversion. But I know that for a while in in 2001 or 2002 Krebs offered the M14 conversion. He no longer does but it does prove that it can be done

That's a good Idea.
If you can weld or have a spot welder you could make the pieces for the front and rear of the mag with a grinder or dremel and weld it to the mag body.
I've done something like this with mags for the TEC9, it's a SUOMI stick mag with diferent locking lugs, I just made a new plate and cut a notch in it then welded it to the mag body. It looked like crap because I'm not a good welder but it functions.

Hope this gives you some ideas.

What I am after is minimal changes to receiver and none to the mag.  M14 mag has a hole up front, so screw a tongue to the receiver accept it (bend or weld on this to get the right shape), possibly make a new latch piece to match the mag at the back.

Perhaps new feed ramps might be needed; easy incremental dremel work.