The trouble with trying to get big dollars for a true classic car like the KB10 is that the potential buyers are quite savvy and know what they are looking at.I mean no disrespect but members on this site where aware this car was on ebay 5 minutes after it went on the first time and going by your photos there are things incorrect and or missing on the car which will cause the collector to reconsider what price they may offer eg.front panel and indicators are from a B10 sedan not KB10 which sugests a heavy punch in the nose at some stage,missing the grille badge (these cost a fortune)also not sure about the seats although they have covers they look like sedan or wagon but will stand corrected.Boot boards and linings are missing,again big bucks.All this is just my quick observation and as previously stated i'm not trying to bag your little car or put you down,but you asked for advice,and this is arguably the best place to get it.Now i did not place a bid on this car but i believe what you where offered was about right for what you have,or keep it a bit longer and get it back to 100% genuine if you can find the right bits and have another crack then.
Cheers Bert