What type of exhaust does your 273 have??? show some photos!!!

What are you driving? If you have a 67 Barracuda, you'll have a hell of a time getting a second pipe over the axle any larger than 2 inches. My exhaust guy thought he could run 2.5", but it bangs against the spring when cornering, and has zero clearance on the tank side.

When they say the single exhaust flows better, that's with that huge "Formula S" resonator, which costs as much as a whole exhaust system itself.