Do you mean a thread clip where you are cutting part of the thread off to allow for easy makeup?
If you do, use a grooving insert. program another threading cycle using the grooving tool and the same thread info. The part you have to play around with is the amount of thread you want to remove. Set your "Z" length accordingly. Now move your "Z" starting position until you "clip just the starting thread and not the second thread. Make sure that you use a M24 before the G76 line.
If you don't understand what I am saying, I can Email you a sample program so that you can see what you need to do.
As far as the rear of the thread, I never had to worry about that.
By the way, I have a Haas SL-30 Big Bore.