Drill new holes???

Like I said, counter productive . . . if you're going to retain the risers, then you may as well retain the manifolds as well, as the GIL risers will only work with the GIL manifolds. Are they jacketed and mix at the tips, or do they have a bung with a hose leading to a separate water dump at the transom as well?

nope just on the riser... I was looking at the revolution marine manifolds?? good? bad?

Why would you switch from GIL to Revolution? Revolution is a terrific product, don't get me wrong - but it was manufactured to be an inexpensive GIL replacement if memory serves me. I don't believe there is a performance gain to be had, and I also believe their flange where the riser meets the manifold is different, so your tails wouldn't work with their manifolds. The owner of the company is a member here - I don't remember his screen name off the top of my head, just do a search.