I am gonna put a flowmaster 40 series on the truck, and best price seems to be in Summit Catalog. They have several listed to fit the f 150, but I'm not sure which one to get. Does anyone know the correct inlet size, and whether it should be "centered" or "offset" Also, If I want to put the duals out the back with the 3 or 3.5 inch tips, how big should my tailpipe be to accomodate the tips. The options are 2, 2.25, 2.5, and 3 on the dual outlet 40 series. Anyone know?

 

I have a Dynomax setup with a 3" centered inlet and dual 2-1/2" outlets. The muffler case is 24" long. I had dual side tail pipes from a Gibson cat back whose baffles broke and have the original 3" stainless tips on them. The tips are from Gibson originally. You ought to be able to do the same thing with the Flowmaster since I believe they have a comparable muffler to the Dynomax I'm using. You can also have tailpipes setup any way you want, dual side, dual rear, etc.... You just need to find somebody that will do custom bending.