You will be able to tell by multiple reasons. The most obvious of which is the israeli markings which usually come in the form of a U symbol or straight up arabic on the left hand sideplate. Otherwise you will have to look at the feed pawl, top cover, and bullet guides for which I am not going into detail about.
The only reason why one should/would by an original .30o6 kit is to have a usgi original for which all of the Israeli guns are built on, but unfortunately marked as which.
We have four left in our inventory two of which are original 8mm guns with the original 8mm feed guides, we are only building them into guns and not selling them as parts kits.
There are a few sources of parts kits available that I still know, one is coles distributing, the other is military gunsupply. Both good companies and easy to deal with. You could also try TNW but I think tim is going to build all of his into guns.