[Excaliber]

Of course it's your call but if it were me:

I'd keep the engines intact, no disassembly. I'd simply state the approximate number of hours and history (as you know it) on the motors and market them. Maybe e-bay, maybe not, thats a tricky one!

It just opens a can of worms to have the motors torn down and an expense you may not recover in the final sale. As DV said, no problem having later model heads, from the factory or replaced at some point during the life of the boat. Heck for you know the blocks could have been bored also.

Make no promises, state the history as you know it, offer them for sale. OR, tear them down, VERIFY everything and sell them "in a box"? Tough call.