i have a 68 camaro with a 406 small block in it and i have 2 pairs of headers, 1 5/8 and 1 7/8.
i have a pair of dart pro 1 aluminum heads with 2.08/1.6, 230cc/64cc, .537 .567 cam. tryin to figure out which headers to install and possibly what size pipe to run to the back also. if anyone has any advice that would be awsome

 

With a 406 you're going to be on the upper end of 1 3/4" for your best primary size. General rule of thumb says 415 ci is 1 7/8" territory, so I'd only go with the 1 7/8" if you're pushing some major RPM (we're talking 6500+ at redline).