When I first mounted headers on my daily 235, mostly V8 race experts said it would make no difference for a stock straight 6.
It did for me, which is what matters after all.
These engines talk in such clear and easy to understand language, no dynos or experts can tell you more than you can figure out by yourself with safe experimentation.
A lot more fun and exciting anyway.
Straight 6 likes straight short pipes.
The easier the engine can breath with less restriction, the better the performance at higher rpm.
For hauling loads with trucks, keep the original simple intake/exhaust for better bottom end torque.
Mufflers and crossovers on a street straight 6 help tuning your exhaust sound for the most part.
Just go with what sounds and feels best to YOU.
Gains and losses in power are too insignificant to worry about in the mid rpm range.
