Hello All, I'm sure this has been discussed before--maybe someone can point me in the right direction--I know the difference between an early (144/170) exhaust manifold and the newer style with doughnut gasket...however, I've purchased one that is listed for a "64-67" 200, and it is listed as a 1 3/4 opening. I know some had 2-inch openings--when did that start? Even if mine is 1-3/4, does it still have more interior volume than the early style?