Yes it will provided that only the muffler was changed out and not the piping but if the piping was also changed out then it's not a big deal to have it custom fit unless you can find OE pipes as well.

Were the catalytic converters deleted/hollowed out? That would create the noise...

 

ON mine: It seems that the previous owner only changed the muffler. There is only 1 pipe in front of the muffler (going into the muffler) .

In a 2010, aren't there 2 pipes going into the muffler?

Here is a pic on mine:

 

I found a 2010 Cat-Back Exhaust from a CC. Now will this fit my 2005 XE KC ?

Here are the pics:

 

It will fit just fine if it wasn't on a 2010 long wheelbase model.

 

Now I see why you say your system is so loud, it's dumped out under the bed. Loud, and potentially deadly as well. The exhaust gasses can accumulate under the truck and be pulled into the cab. Should at least be routed out the sides.

 

i have a 18"magnaflow that i'd be interesting in trading ya but i can't have my truck without a muffler during shipping... mine has a single turn down similar to yours