Some sort of recoil management, if you need it, and a decent optic. Take the rifle out and shoot it. You will figure out what you want to add or change on the rifle as you go. There is nothing like driving a full custom rifle. With that said it is not what you have to have to shoot accurately out to a 1000 yards. Hopefully you hand load. That will help get the accuracy out of your rifle.
Don't let guys tell you that it is too big or not good enough or any of that other stuff. Lots of guys here that are shooting factory rifles in moa of deer out to very long range. Good clear optics are more important than high power.
Have fun with it.
Steve