IMO - who built it, what was done, and what parts were used is everything. Without a reciept and being an already pulled motor there is no way to even confirm mileage on the motor.
Is there any way to get in touch with who built it to see if they have a copy of the build sheet in their records? Without that I would say either sell it to a friend, or to most it will be just a used motor. As Mark said "they all ran good when parked". That's something you hear from almost everyone selling a motor. I sold an 1800 motor complete with the top end (I was told) rebuilt by the Bug Shop for $400 last year or the year before.
Really don't know what to say for price for you but $1800 is very high if you are missing all the vital info. $400-$800 range? Just list it and keep lowering the price untill it sells I guess.
BTW I am not trying to knock you down either...just trying to be helpful