The 6 doesn't seem to be rare in the sense that it's a desired option. I think what is more rare, is that it's all there, though it is rusty. You have the original trim, uncut dash, complete top, etc.
The question for you is do you want to start here? Me, I wouldn't because I like driving mine and wouldn't have been as into the blazer if I started with what you have. Nor do I have a shop/garage to do the body work myself. So even at a $1000 I would pass.
Also, did you check the windshield frame too? That's a really common area of rust. Up until last year there weren't any parts for that, and still, it's not a complete part, so you would need some existing windshield frame to attach it too. Often if the outer rocker is that bad, the torsion box will be shot too.
If you want to see some sample prices of a place that sells the "better" replacement panels you are going to need, go here:
http://gmcpauls.com/Patch_Panels.htm
Stay clear of LMC panels.
Then you can start to see how much just parts are going to be for the restoration. Which obviously won't include the massive amounts of labor required.
If you want all original and can restore it to stay that way, that's a cool find. If you want to just drive it and build it into a off road rig, then I would look at starting with a less rusty shell.
-Jacob