Anytime a situation like this comes along, take your time to analyze everything. Don't be too quick to say yes or no. If a guy was offering 8K for a bike, I would have told him you NEEDED at least 10K or more just to break even, then negotiate from there.
I don't want to take the wind outta your sail, but if your engine doesn't already have the reliability mods, then that is more money that will (or should) be spent during the next rebuild. It may have to be done to any other zilla you pick up, or it could already be done. Who knows...
But of course if there was a strong bond you share with your bike, then no money in the world could separate you. That is how I feel about my deVille. I've already turned down a trade for a brand new Cadillac XLR + cash. I can always go to a dealer to buy the XLR but it would be a bit difficult to find a 1959 Sedan deVille in good shape.
And as for my zilla? That heartache would be gone in a heartbeat!!! lol