the spark plugs clear the 2" tti headers quit nicely on my set up; actually better than stock iron heads.

yes, they are butt ugly.

as far as power increase goes; they are only as better as the old heads are bad. in my case I consider them a power loss.

I think some of the hype surrounding the the edelbrock rpm heads may be exaggerated. I don't consider the ones have as anything marvelous.