Been doing a little research and found that the gen-5 Camaro manifolds most likely won't work.
Here's a single post from a thread on LS1Tech.com showing the interference. The exhaust outlet dumps pretty much straight into the rear lower control arm mount bracket on the frame, at least on the passenger side:
http://ls1tech.com/forums/15843222-post10.html
Looks to me like a pair of Hooker cast exhaust manifolds are the best bet, made from High Silicon Ductile Iron:
http://www.summitracing.com/search/p...aust-manifolds
Very reasonably priced at 307.95 with free shipping, about the same cost as the RARE Ram Air D-port 1967 GTO A-body exhaust manifolds I used to run on my car with the 455.
I plan to save some money and get the bare version rather than the ceramic coated ones, some POR-15 exhaust manifold grey paint is about one-fifth the cost and very durable. Most ceramic coatings on exhaust manifolds just end up disappointing you, they usually end up rusting within a year.