I believe this is what you want.
Sanderson Block Huggers
I have a similar issue with my 5.7L. I need to run my right exhaust straight down and under the pan over to the left side. The only stock Chevy manifold that does that is what they call a Ram Head. However, I don't think the Ram head will work on the left side because my power steering pump depends on the exhaust manifold bolts.