Great story on this DZ reunion, I have the same problem. I went to look at a rusted out 69 convertible and ended up buying a DZ short block (std bore) from the guy, which had under 12k miles. His dads friend used there garage to swap a 327 Fuelie in the Z/28 in 1971 and left the DZ there for using the garage. It is a early LOS stamped vin on the deck surface (so same deal, helps with proving its a Z). So I did a vin search and yes I found owner, I have not told him I have the motor because the first thing I ask was the car for sale and he said "maybe". So that was the magic word. If he said no it's not for sale, I was ready to sell him his motor, and I was hoping I was going to be fair at $5,000.00 , which I had paid $2,500.00 for it this spring. I'm still waiting him out, I left him my phone# when he comes up with a dollor amount. He told me all about the car it's Cortez silver with 713 houndstooth, he know is a Z but he said he can't prove it because the original engine is missing, at this point I was bitting my lip! I need to call him again to nail down a $ , but back to your deal I think $5000.00 would be real fair for both of you. I was thinking 5K maybe a little high a first on my deal, if I decide to sell it to him, but after reading all this it sound fair. Good Luck this is fun stuff !!!