Finally decided on a cam for teen SB. Should I bother with header?

If your not changing the springs, I wouldn't waste the time or money on a new cam.
Whatever cam you use it should be for torque only in
those rpm parameters.

I think your fun(ds) would be better spent on a quality torque convertor in the 2200 range.
Imho your dual exhaust and manifolds are fine for what you have.