Engine Choice for a new BDR?

[Dumpling]

It's in perfect condition with about 5000 miles on it. Never raced, street driven only. Genuine Ford sideoiler block, not a service block. Genuine Ford MR heads. Forged Ford 427 $ crank, LeMans rods. Forged pistons. Solid lifter cam of unknown specs. Original Ford aluminum MR dual quad intake. Dual Holley carbs, not sure which ones, but I believe they're original (not re-pop's) BC/BD carbs. I do not know many part numbers nor dates yet. The engine was built with as many original MR parts as possible. I know this isn't a lot to go by, but if anyone has a super rough ballpark that might help for now. I want to make sure her expectations are within reason.

Right now the engine is on a stand in the garage. He turned it over by hand on a very regular basis, as his plan was to soon buy another Cobra to put the engine in. How to best sell this - leave it assembled, or tear it down to show what parts are in there. It's a shame to tear it down as it's in perfect running condition and it's tight. However, I understand that buyers may perhaps want to see what's in there. Sort of a damned if you do, damned if you don't scenario.

This guy is looking for a value...$12K has been suggested.