Ok, so it's summertime and I'm finally getting around to doing some work on my truck. I'm going to do pacesetter LT headers w/ original cats, magnaflow 3" in/out cat back, and a custom tune from wait4me. That should wake the 5.3 up quite a bit

Anyways, my question is if I'm keeping the cats should I get the offroad y pipe (82-1176), or will the exhaust shop just weld something up?

 

Let them fab something up for you!! No need of hacking a new Offroad y pipe

 

It's going to be tough to use your original cats since there isn't much room down there to begin with.

One other consideration is that your stock cats are 2.5" while the ORY is 3".

 

Hmm, Kingpimp makes a good point about the stock cats being 2.5". After a closer look at my emissions laws I think I can get away without any cats.

ORY pipe it is then.

 

I might be mistaken, but an ORY is a catless y-pipe. It is a replacement piece. And if you are going to go catless, you will need a tune to delete the rear O2 sensors or get simulators.
If you do decide on going catless, just have the exhaust shop fab a y-pipe. Regardless of going catless or not, the headers may be off a little and fabrication will need to be done to your stock y.
And while you are at it, decide if you are going to run cutout(s). If so, get them now and have it done all at one time.