If you use Lee dies you will either have to put the locking nut on the underside of the toolhead or turn the lock nut over(rubber O-ring side up) to get it to work on the top of the toolhead. I do this with no problems.
If you will be using cast bullets at all I would definitely get the Dillon dies. Their seating and crimping dies have clips that allow you to disassemble and clean the dies and then return them to use without having to readjust the dies. A very nice convenience.