Not sure if anyone makes what you're looking for or about other manifolds that will work. However, you could make your own headers - I think Summit or someone sells a kit.
I think I'm going to work with manifolds for now- Online is a great dyno report (Mopar Action perhaps?) of a crate 360/300hp motor run with everything from 318 manfolds up to top of the line headers.
25 hp & 25 lb/ft of torque was the maximum difference between best and worst. I can live with that. I'll see if I can find the link and post it.
If I can wedge the magnum manifolds in there I'll be fine and the 5.2 will flow less than the 5.9 dynoed.