It looked like an off the shelf 1990 W250 Dodge downpipe would work for me but the only thing I could find was a 4" one. In the end it still needed to be modified but no one can say I have a restricted exhaust. ;>) It goes into a 4" Flowpro "Twister" resonator and then for the moment goes into the stock Hemi 3" duel exhaust. Once I get it running and tested I will replace that with a 3 1/2" Ecodiesel Race pipe. The stock Cummins exhaust is next to my new downpipe, quite a difference in size.