454 dually header/exhaust question

[THI]

If the O2 sensor is anywhere downstream you need a heated O2 sensor to operate properly (with or without a cat). If emission testing is not an issue (you mentioned no cat) I would go with one of the dual exhaust kits and get a collector that has the bung for the O2 sensor and wire in a heated O2 sensor.

The factory 454 TBI exhaust had two choke points, the factory "Y" pipe overlapped inside where the two pipes met, and the stock muffler choked down to 1-7/8" just inside of the 3" inlet. Because of excessive heat the converter was placed after the muffler. The exhaust manifolds themselves were not bad considering they had a 2-1/4" outlet. I mention this because if your system is using the original "Y" pipe cut to fit, you have the issue of the overlap at the connection of the two pipes.