[68 C10 Driver]

Given what I see in the photos, and that there is a little rust on the doors (looks as if that is inside-bottom are easily touched-up without damaging exterior paint), I would say no less than $20k. The rain gutters can be repaired, hopefully the rust you see is just surface rust. My truck was nowhere as nice and the seam sealer around the rain gutters was cracked, you could see rust. Cleaned out old seam seal, removed surface rust, and a careful repaint/blend into the roof should net great results. My truck sat outside for 15 years in Georgia before I rescued it.

I think your truck is a gem.