I am wandering how tight a fit is it to install the 51" Nelson/Donaldson muffler with the cat. I have the 2004.5 LBQC. Thanks!

 

Take a look under your truck and notice how the stock muffler is held up by the hanger rods. Also eyeball how the incoming pipe is offset from the tailpipe section. Then look at a nelson or donaldson muffler in a different way since you want to keep your cat . Reason I went MBRP from turbo to tip

 

It is very tight, and can only be done with the LWB truck if you want to keep the CAT. I should have some pictures in my gallery of the Donaldson 51.

 

I have a Quad cab short bed 2004.5 and a 51 inch Nelson and it did fit with the cat. It is tight.. the muffler shop had to cut the pipe right after the cat. Sounds great! I will try to get some pictures.