I think Gardner is the best source for stock exhaust, but Pypes and Ram Air Restorations sell systems also. Stainless Works sells a 3" system for header cars. Original style '67-68 splitters are avaialble, but I think they cost around $280. They are a complicated, but poor design.
Exhaust is the last major thing for me to tackle so I've been studying it. I should be getting one of the first prototype 2.5" X systems from Ram Air Restorations made to fit under the convertible bracing. I'd like to run splitters, but not the factory 2", $280 dollar versions.
Has anyone adapted the later style TA splitters to a '67 or '68?