Hey Michael,
I see '90 C2s often for under $20k, sometimes under $15k. If you are looking at a rebuild, that is expensive (as I am sure you know) so to me personally, it's not worth that much.....maybe a little more if you already have a cheap(ish) motor lined up.
Otherwise, I wouldn't want that for any more than $8-10k. There are just too many others out there at sub-20k ranges.
just my opinion of course
-Chris