I believe the exhaust manifolds are different on the 74 and 78. The 78 has the split-manifold design with the outlet on the rear, while the 74 has the same style as the 108/109's - single manifold on the driver's with the outlet in the center, and dual manifolds on the passenger's side with the header pipe joining them together.

Basically, you'll need the entire system - the manifolds (3 pieces), engine pipes (two pieces), and then the resonator and muffler (two pieces).

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k