We put a home made 4" system on my buddies 93 W350. We used the Cummins special down pipe because of the Jake, then an adapter up to 4". The rest we made from elbows and straight pipe cut to fit. All joints we sealed with stainless steel band clamps. There is about a finger width clearance around the T case. We used an MBRP muffler and just a down spout. It is a service truck and he didn't want a tail pipe. When we changed to a 16cm exh housing it was easy to take apart and re do because of the clamps. Shadrach