Ok so as of now I am running an open stock downpipe. I have plenty of 4" pipe laying around with a 45 bend and a couple 90's. I am wanting a very inexpensive exhaust and right now im thinking of just using an adapter from the stock downpipe to the 4" and dumping it out in front of the rear tire.

The truck will not be modified other than the signature and possibly some RV275's in the future.

Do I need a 4" downpipe? and if so what are my choices? I know rip rook has one available for about $90....what would I need to have someone fab my own out of the 4"?

 

With what you are running the stock downpipe should be fine even with the RV 275s. I have had exhaust exit in front of the rears and it was loud and cool.

 

Use an adapter from the three to four inch pipe, makes it alot simplier. I tried one tapering the pipe with cuts on the end and it was a pain. If you run straight over the axle you will have enough bends probably. I have done this on two trucks without any interference problems.