Fair price for a '70 340 engine that needs rebuild

Hello All,
I have a 340 motor with a date code of 10/69 (1970 motor cause of late date?) The engine is all there except a carb and distributor. The short block needs a rebuild(has original bore). The heads were redone with three angle valve job and new, better than stock springs. This was done over 30 years ago:eek:. (Life got in the way) The heads have been stored in a climate controlled room, soaked in oil and wrapped in plastic. They look like they just came from the machine shop..:)
I have someone that is interested in the motor but I don't know what a fair price would be for this motor. I don't want to gouge the guy, but I don't want to give it away either. I looked on several different sites, Ebay, RacingJunk, etc., but there wasn't really much to compare to.
Any suggestions would be appreciated..:thumbsup:
THX..AL