If you are going with a push/pull on the volume or tone knob, it's pretty easy. All you'd have to do is follow this diagram:
View attachment 3569609
But if you wanted to do that with pan pot, it becomes a little harder. The only way I've done the pan with s/p has utilized an MN TAPER POT, which you don't ground. I'll have to draw something up for that.
And if you're trying to do it with the stock preamp... I'm really not sure how I'd say to mod that setup. It's been a while since I've seen one. Depending on how crucial the stock pots are to that layout, it may not even be possible.
But yeah, if you ever need any help with one of these, I'm always happy to help.