Go with a flip-up front BUIS, as when using the scope at a higher magnification, you will not have any ghosting that occurs with a static front sight. GG&G makes a great one, but a bit pricey, so I who suggest a Yankee Hill.
As for a rear BUIS, one determining factor is the size of the rear objective of the scope. Smaller the profile of the BUIS the better obviously. Knights 300M and 600M will do fine as well as the ARMS #40-L and Troy.
Eye relief of the optic is another concern, so a mounting platform is of upmost importance. Generally, Leupolds have very forgiving eye-releif so the scope will need to be mounted further forward than what the flattop can accommodate. A cantilever design mounting solution would be your best bet. Options are the LaRue or ARMS #35. I would stay away from Armalite's unit as it weight entirely too much, but it is a stout piece of gear.
Lots of info avaialble, but typing with one hand has slowed me down .