Will a 3 screw Schaller bridge fit the Fender 5 hole spacking
 

I searched already.

You'll likely have to plug the holes and redrill new pilot holes, but aside from that, yes.

This will sound like a flip answer, but it isn't.

Only the middle screw will work with the original screw holes. You'll have to drill the other two.

also, why bother?

is this the schaller roller bridge? those things are tone and sustain sponges (assuming you hear any difference at all).

Not my experience. I've had good luck with them.

fair enough; the loss is more obvious on the roller guitar bridges, especially the tune-o-matics.