Thirdgen ls headers
Mine are 1 5/8, but for the price I really don't care, better than manifolds and the Hawks are a hose job and they want like another $450 for a y-pipe.
Some folks have been posting that the new version of them are indeed 1 3/4 however.
Check out the Lt1/Ls1 swap section at thirdgen.org, someone may have posted pictures and measurements of the new version

