That part about "...and what are people most happy with?", I think you'll find the answer is stock manifolds - regardless if it's an AMC or SBC, etc. I had headers on a 360 - sounded great... when the gaskets were in tact. Similar to Matt's experience, the uneven surfaces, loosening bolts... the gaskets were an issue. And yeah, rust. Unless you drop a chunk of $$$, they're going rust.
1981 CJ8, Chevy 5.7, SM465, D300, RE 4.5, 35" BFG MTs, 20/30 4.56, Detroits, Warn 9500ti