Are you into extreme restorations ?
That looks too far gone to me for the average Joe to rescue.
There are very few S12s around, parts availability isn't great and they have such low values when restored that its not going to be possible to do anything with that that would be commercially sensible.
If it has great sentimental value, you have awesome welding skills, you have great contacts for parts supply and specialist restoration skills and you are looking for a project to end all projects then maybe...if you have bags of tenacity, you could turn that into a nice car.
Otherwise, I'd look for a better base and see if this one has any salvageable spares before consigning the rest of it to history.
Sorry if that seems negative and harsh but it looks more fecked than a very fecked thing to me.