How the insurance companies assess the buy back value, is they know how much a normal bigger salvage yard would give for the remains.
For example, I live in Idaho. The yards don't really care how built a sammy is. To them it's just an old Suzuki that they don't see oftem and presume is pretty much worthless. To them, an 87 sammy JX is worth about $250. I got in a pretty bad accident in 01 with a heavily built sammy, a fullsize Blazer pulled across my lane in front of me, no warning...his fault. I hit him, and long story made "Readers Digest", I flipped on end onto my roof. Destroyed my truck, hurt me pretty good. State Farm was the other guys carrier. They said the value of what was left, buy back, was about $250. Which is cool, cause I ended up getting about $6800 just for the truck, and I got it back. I was into it quite a bit for parts, and got most of the parts back. So far, the engine has been in 3 other sammies, including the lwb.
I think if you stick to your guns, you should be able to buy it back for $5-800. Hope that helps.