Read that great 66batmobile.com site. It has the stories on each car. One was a 4 speed. Another one had a dual quad 427 medium riser set way back under the cowl. That was the drag car.
George was up here at a car a couple weeks ago and I had lots of time to chat when he wasn't busy. He says he did offer his cars for drag race exhibition cars but that only lasted the 67 season or so.
That site also mentions a replica being built by a guy in Quebec and George "aquired" it later on. I assumed that meant maybe won it in a lawsuit so I asked how he ended up with the car and he says "Well they were passing it off as a real Batmobile and it wasn't..."
The "letter of authenticity" is authentic , not what it's saying.