I don't like routing either, a while back found the HB sized Mean 90's that just drop in, so that part is easy. Since the Epi 339 with P90's and the new Headstock isn't available yet, I got the one with humbuckings. I most likely wouldn't do this mod to a Gibson, although I did replace single coils in Jr's and Melody Makers with humbuckings back in the 70's, these were pawn shop guitars that I thought I was improving.