I assume you mean the AA864 circuit? That's a rare bird. A lot of tube charts for AA864 are out there but that doesn't necessarily mean that's what's inside. The only way to be sure is to check the circuitry. I've seen way more amps modded to those specs than I have actual AA864's.
Sorry I can't help you with any dealers. Just make sure you're thorough with your questions. If they won't open up the amp for you I would be cautious.
You could try Savage Audio in MN. Word I've heard is they're whittling down their massive collection of vintage amps. I'd guess anything they have has been well cared for, although my interactions with them have been limited.