I had a 68 Camaro with a 406 and a turbo 400. My friend and I(mostly my friend) was able to get a B&M shifter to fit in the console. I think it was the Quicksilver. The silver part of the base(we didn't use the black part) fit great in the console.
I'll 3rd that one. I have a B&M Quick Silver in my 69 on a TH400. I fits right on the console. Buckeye is right, you ditch the lower black part and just use the nice silver cover. All you need to do is fabricate a top support plate out of sheet metal which is really easy. I like mine a lot, no missed shifts ever.
I too like the quicksilver, I've tried several others and this is the most easy one to use. I think it's the pro-stick shifter that a freind of mine has, and you have to pull something or press something to get it into drive, why would you want that? He just put the shifter in and was racing the car and forgot about that part, and almost over-reved the engine. The quicksilver has no handles or levers to fool with. I've heard some people complain that you can't go directly from drive to low, but that's not a concern of mine.
68 468 700R4, and here it is; mutert23