Rate what this 72 k20 burb worth

[titan1587]

I have the chance to buy this it's a 1 owner 72 3/4 ton fully loaded a/c tach even the chevy wheels not a thing missing. Barn doors. Only rust is the rockers below the doors that's it. 350. Turbo 350. Original paint not perfect but no rust besides rockers and nothing major. Runs great and drives great 140k miles original.

What do you think it's worth or you'd pay for it. Then I'll tell you what I have the chance to buy it for is?