I'm looking to get a somewhat more knightly look to my black templar terminators while still keeping the armour fairly standard.

The plastic grey knight terminator heads look like they'd do the trick, but does anyone know how well they'd fit? I've made some unsuccessful attempts to adapt regular power armour heads to fit the plastic terminators and would like to know if its worth the time, money and effort before ordering a bunch of GK head bits.

Pointers towards other sources of suitable heads would also be greatly appreciated.