Are most gb mini's out there for sale more likely to be the newer version or the older version?
If you find a GB version of the Mini-14, it will be among the older versions you mention. The closest thing to it in current production is Ruger's Tactical Version of the Mini-14. The most notable difference between the older and the newer Mini's is the change Ruger made in the barrel. The photo below shows this difference, which is most evident directly forward from the gas block. The change was introduced as a means of mitigating the "barrel whip" condition commonly experienced with the traditional Mini-14 barrel. But, don't let that cause you to give up on a GB or other older version. Accuracy issues can be resolved, and without spending much money.
Incidentally, I believe J & G Sales already sold out of the surplus LE GB Mini-14's they were offering, but I notice now that Gallery of Guns (Davidson's Warehouse) has the tactical Mini-14 on sale for the entire month of April...$665...