5.9L Magnum questions

that would be my choice for the set up/parts that you have to compliment it.

with a 3.55 if you put wings on it that early a would fly.

put whatever exhaust you have on it while you save for headers. no sense in making a half step with whatever combo of manifolds for minimal gains.
Been looking around at exhaust options. As far as headers go, I think the Sanderson DD9's are going to be my choice. Kinda cheap, and I hope they flow air better than iron manifolds.