I have experiemented a bit with exhaust on my daily late 235.
Basically, as previously mentioned, you want your exhaust to match and be optimized for your driving habits, as there is always a trade off and one type of exhaust will not be ideal for any condition.
For freeway driving I found open short pipes cut right under the cab allowed the engine to breath best and give most power at prolonged higher rpm.
Pipe diameter should be 2". You can add short non-baffled straight-through mufflers (steel or glass packs)to reduce the violent loud noise down to levels you can accept while driving.
24-30" is quiet, especially at high rpm when the pulses get smoother and more monotone.
For city driving the 235 with dual exhaust likes 1-3/4" pipe diameter and you can rout them over the rear axle and out the back.
This will give you better low end torque, after stopping and while accelerating.
Use whatever mufflers that sound good to you.
I also believe the closer the mufflers to the engine, the louder the sound.
I drive equally on freeways and in the city, so I have 2" pipes with 12" and 17" steelpacks.
