I have a set of R028023 exhaust manifolds that fit any GM LS style engine. They're a center rise manifold. I had originally planned on adapting them to/for a turbo, but have since then changed directions with the build. Brand new, never used.
I was surprised at the relatively free flowing design of the runners. I'll snap some pics next time I get over to storage.
May take a while to sell these, but they will be a great deal for the right guy doing an LS swap into their lake hot rod. You can fab up a custom riser, put a turbo on them, or purchase the riser that's designed for them and run hose to your existing 3.5" through hull exhaust... about $165ea