Driver side cat started rattling and engine has periods of stumbling. Took truck to a shop and they quoted me a price of $700+ for just the replacement part. It appears that it is an entire Y-pipe assembly that has to be replaced. Driver side unbolts from header, passenger side unbolts from header, and single pipe unbolts from just in front of the muffler. Is there an aftermarket cat that is specific to this model that can be welded in or do I have to get the entire assembly?

 

If it is a Single converter on each side, then YES there is, & you can save some money.
The AP # 608326 works for Federal standards. California models Magna-Flow has one, I just do not know the part # off the top of my head.
Technically there is weld-in replacements for the 4 cat system as well, but there is no real price savings.

 

Yes, this is a 2 cat system.

 

Cats are covered under the emissions warranty - if you have less than 80k miles on it take it to a dealer.

 

What state are you in?

If over 80k miles, you can have to Magnaflow cats welded in on both sides for much less than that quote. But I also have my factory cats that I'd almost give away if you're in Texas.