You now have the opinion of a proper expert!

If it's not your grandfather's "werks" ST/R RUN!! :D

if you want a # matching concours masterpiece, find another.
but since you already have a nice engine it might be worth saving.
the problem with longhoods is as they increase in value, most are unwilling to modify.
sadly this car is in poor shape and not worth restoring as a collector, but as a race car, maybe.
the floor and tunnel can be repaired, how are the suspension points?
the front are an easy fix but the rear torsion bar tube is a difficult repair.
and double check the longitudinal repair, if solid with good suspension points, i'd say go for it.

I'm trying to run. I found rust inside the longitudinals. If I can't sell it, maybe I'll work it into my life but I'm not too happy about having it today. We'll see tomorrow.

And found that a previous owner patched the rockers with bondo at some point. wow.

Sometimes some must die so that others may live!!

Run Forrest!

The challenge to do something "just because it can be done" is often tempting, but in this case, outside of special provenance, I just don't see the upside. Yes, it can be done, but if you want a race car or something, you will be streets ahead finding an SC shell/roller and building that up. To do this car right, the cost (and time especially) will be high. The link posted by sfoster13 is very instructive (and its worth noting that that shop had everything, including a Celete). How much of that car did they actually keep? This car may even have less good metal.

I have yet to see one of these older cars where there wasn't a whole lot of other rust issues than were initially apparent. It sounds like you are starting to find them (i.e. the rockers).

You are the one in the best position to judge though, and good luck whichever way you choose!

Part it out and crush the remainder

I ran.....I ran so far away.
Some one else is going to do something with it now. I'll keep my eye open for something else. Someone with a good roller?