cutting the steering shaft.

[sams60gmc]

So I didn't buy a kit or anything for my powersteering swap so I'm kindof lost on where to mount my box. I've read a couple of different write ups on it but when it comes to mounting the box there are a few different measurements for where to cut the shaft and how far to move up the rag joint to put it in the proper location. So my question is. If I cut the rag joint off right at the top how much of the steering shaft do I cut off and how far do I move the rag joint up the shaft to get it into the proper location. Thanks for the help.