I would ask him how he knows it's a 390. Unless he's been inside the engine it's anyone's guess. Just to cover yourself as it seems every 352-360 turns into a 390 on sale day. And he didn't post the VIN. You can measure the stroke easy nuff which I'd certainly request. A lot can change in some 40+ years. That's a pretty good chunk of change and you want to be sure it's what you want. Rest of the truck looks pretty nice. It's a solid $3k ride anyway.