Here is a nice looking GS for sale 1970 BUICK SKYLARK GS 455 - $17500[SIZE=-1] (VICTORVILLE)[/SIZE] img
I cannot see the car from this computer but thats where the forced flow switch is on non ac cars that came equipped with that option
Looks like it's got a factory am/fm, so I'd bet on them being to switch back and forth between the factory unit, and that aftermarket thing on the trans tunnel. Also noticed that factory in-dash tach, and the Olds emblem on the horn button.