i think the poles on the f-spaced (trembucker) are supposed to fit better with the distance between each string of fender guitars, but ive also heard that it doesnt matter at all and makes no difference,
On my JS i have a ''normal'' (not f-sapced) humbucker JB, the lutier who install it said it sound the same as a trembucker, but i never really knew if i got rip off or not . .