Hey sorry for the late response.
As funny as it sounds I ordered a 10778 about a year and a half ago for my camaro (before deciding to go true dual) and just found it this weekend. I knew I ordered a Y pipe, and thought to myself "You know what would be funny, is if its the same one I can use on the truck" sho-nuff.
Anyhow I pulled the muffler off today to look at how much of a pain in the ass it would be, and I think I can just cut some pipe up myself to do it (I already have the 2.5 inch pipe, just need a few adapters for 2.5 to 2.25)
Couple of questions for you;
-Did you only have to "bend" one pipe? Hard to tell from your pictures, but from the Mufflex picture Ive seen it only looks like one of the 2.5's are bent. Im just unsure if the Ypipe is the same?
-How much did it have to get bent out? I compared the spread of the Y to the muffler and it seems the muffler is about half an inch wider?
-Any reason for adding the chunk of 3 inch pipe? I was thinking about cutting 2 slits in the 3 inch side of the Y-Pipe, and clamping it directly to the pipe thats already on the truck. That would save me having to buy more pipe as I already have about 20 feet of 2.5
Thanks for the help