headers or not to headers

so if I understand all of this well, I would be better keeping my stock manifold on my 318, then going through the install of cheap headers.
It's a stock 72 318, will be 4 bbl and dual 2.5" exhaust pipe ... and that is it.

Will the Durango/Dakota manifold fit and improve something, in a 72 a-body with p/s and p/b?