That was actually going to be my next question. Use the .311 bullet in the .308 case. A friend of mine loads .308 by the truck full, I'll ask him to make me up a few hundred.
As far as pressure, the heavy M72 barrel should be strong enough I think. My old G3 had less meat at the chamber and did it all day long.
On the other hand the Romanian RPK I have has a chamber diameter of .905 and the Green Mountain M76 barrel has a OD of .907. That is good bite and add a barrel pin it should be great. RPK furniture on that with a PSL receiver might be nifty.
But back to the Yugo M72, I believe I will go the route of the .308 with the .311 projectiles.