I have an 07 Quad Cab 4x4 with a 4.7l. I want to get rid of the stock muffler and resonator and replace it with an 18" magnaflow and Y-pipe. My question is what sizes for the inlets and outlets do I neet and what offsets are needed on the inlets and outlets?

I plan on keeping the stock exhaust look, with the single tail pipe exiting behind the rear wheel. Thanks.

 

To the top...been using the search and haven't found the answer yet.

 

For best performance, I would take out the "Y" completely and run the 2.5" pipe from the cats all the way to a DI/DO muffler (or DI/SO if you are set on single exit). To directly answer your question, the pipes out of the cats are about 2.5 inches, so a "Y" with 2.5" in and 3" out would work fine for you. Offset on the muffler really does not matter.