you can remove the metal hold down but I wouldnt recommend it cuz you can bend the socket pins when removing the cpu may stay stuck to the wb and fall off when removing it and the plastic part where the pins are in doesnt come off
and since the AsRock Z77 Extreme 4 has the 775 holes you wouldnt need the mounting kit
edit: forgot to say i been running a 775 since 1366 also this one
http://www.newegg.com/Product/Produc...82E16835708019