spark plug placement

I am running a set of Dove heads with Garrett bushings for 3/4 x 14mm plugs. I am currently prepping replacement heads. I wondered if, by using bushings without the holes,then machining those in place, I could gain any advantage with different plug angles or placement in the head? I believe there are smaller od plugs in use that would allow more leeway as to moving them around a little. We run a 15:1 cr and less than 6k rpm. Have to stay with these heads, but I'm allowed to modify them and am looking for any edge!
Thanks Guys!
Perry