Z owner or Z wannabie who wants a TT and knows the NA rear end provides faster take off, then yes $10k is doable. But that all depends on the market in your area.
If you have a dyno or get one to back up the mods, then I don't see a problem starting the price at $10k. All depends on who rebuilt the engine. Test the market and lower the price a little at a time. Laugh off the low balling pikers.
Not worth painting, it doesn't sound that bad for vehicle age. I'd leave the paint to the next owner.