The black keys look cool but you will not have a complete set I think. You will have to keep using the original AT enter key and shift keys, and probably space bar too. (Unless you modify your AT keyboard to ANSI layout, but even then I think the space bar won't fit.)
I am using an F122 with black keys donated from an M13, but I have noticed that the black keys feel a bit more 'gritty' than the smooth pingy action of the original F122 keycaps. So I am considering swapping them back again.