So, in a now lost previous post on the subject, I had acquired some Corvette LS3 manifolds and some Hooker Block Hugger Headers. It turned out that both of these are unusable. The LS3 manifolds would be superb but the steering shaft cuts across the collector opening. I even bought a milling machine to make a wedged manifold to downpipe flange, so that a downpipe could be angled against the manifold, but this wasn't enough.
So, I had decided it was time to just pay an exhaust company, and I got in touch with one of the best, but they've not got back to me so once again I have been playing today. I cut up one of the Hooker headers a bit, but still it's no good (it's actually the engine mount that's in the way on that one) *However*, I have a better idea of what would work now, and I think I'm going to buy some Edelbrock block huggers, or shorties, or even both. I would be extremely frustrated if they didn't work though, since there's only so much money I can throw away like this.
I have two options, and I am leaning more to these: (65763 / 65762)
but there are also these: (65173 / 65172)
Thankfully that's a pretty helpful diagram on the first one so I'm going to take some measurements tomorrow.
The first ones (the bigger, block huggers) are $415 from summit.