If you can find an original Corvette 235 dual manifold, it's got the same heat riser system the single-pipe manifold uses. They're scarce and pricey, however. A good welder can build a split exhaust setup from a single, but it's not as effective as a factory or aftermarket dual system.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!