I am trying to find out how much of the exhaust system has to be fabricated. I am asking because my current exhaust is going to ****. The previous owner had a Flowmaster put on (it makes my 3.1L sound good, so I'm not complaining), but they used the original pipe from the cat to the muffler, and it is rusty and has a hole or two in it. Then, the other day my driver side tail pipe hanger broke off again. I think its time for a new exhaust, but I don't want to go spending money on a cat back if I can't use it after I get an LS1.

 

Of course you can use it...but is it worth it? Hell no, youll be hurting a lot of potential hp from the ls1. If your running 2-2 1/4" pipe youll flat out be choking an ls1. Besides if you are actually serious at looking at getting an ls1 i dont think you will be keeping the stock exhaust.

Do yourself a favor and just get a 3" catback and find a way to attach it to the current cat converter. I mean no matter what with an LS1 in there you will have to do some modification to the exhaust but with a 3" catback you wont need to worry about replacing catback again. Y pipe and the dinky old cat will need replacing when the ls1 goes in though.

 

I reused my slp catback. had to cut the pipe even shorter than when I had long tubes but yes, pick a good one and go with it