so how do you cut the r/t springs safely? And how can you tell how much to cut?
You can measure the amount of drop you want, and cut a little less than that amount, maybe even half that amount. It's guess and check until you get it right. If you start out cutting too much you can't go back... Cut with a cut off wheel, sawzall, etc... and do so slowly, do not get the spring very hot it will ruin it. Do not use a torch. You should be able to cut to the point where you get a 2" drop safely, any more than that is iffy.
EDIT: Just to reiterate, this is for the rear RT springs only (as far as I know). Not sure if any other versions of the springs have the tight coils at the top. I have been thinking of doing this on my truck this weekend, we will see how much extra time I have sunday...