I removed one from a 68 Parisienne ragtop years ago. It's in pieces, but if you really need me to I could piece it back together to show what it looks like. The ashtray mounts into the whole assembly.
I don't know if its the same for a 68 but I acquired a similar 8 track player for a 67 using the ashtray ring mount and it interferes with the console. (8 track unit is too deep.) I kind of think you couldn't get an 8 track with a console but I stand to be corrected.
I can't speak for 67, but I know for 68 the top forward hump of the console is removed, then a flat plate is installed in its place that should allow enough clearance for the Pontiac 8 track. A similar flat plate is used in 69 & 70 2+2's as the Pontiac 8 track mounts on top of the plate.
The awkward thing here is we're mounting a Pontiac 8 track player in a car with a Chevy Impala console.