-Any suggestions to which dies to use loading for 264 mag ?-
Not really sure what you are asking. You need a Full Length sizer and Seater plus a neck sizer if you want to go that route. If you mean what brand of dies, none are magic. We all have our personal favorites but, fact is, they all work fine.
Ain't no die made nor any handload made that can prevent gravity from working on a flying bullet so hold over at 450 yards will remain a fact of life.