I was looking at getting a hooker cat back but there are two systems for early 5.0. The HO and the non-HO. Does anybody know the difference between these two. I was thinking that maybe one had a different muffler or something. And if i bought the HO (i suppose for the L69) cat back would it fit on my 82 355 trans am which was once a lg4 (non-HO). Thanks.

Heres a link to JEGs with the different systems.
Super Competition cat-backs

 

Im pretty sure the only difference between the two is the flange that connects to the cat. Either its slip fit or bolt on. If your gonna do something different than stock - ie no cat, or can weld and fix it to work yourself, it doesnt really matter. Ask the tech support people at jegs or summit, they will help you out.

 

You are 100% correct. The cat-backs themsleves are idetnitcal. The differences lie in the way they mount to the cat. The non HO kit has a 3" to 2.25" reducer that bolts right onto the stock cat. The HO one has a 3" to 2.X reducer along with the appropriate moutning flange to mate with the stock cat. If you are replacing your whole exhaust at once we always reccomend getting the TPI application cat-backs. That way they don't come with any sort of reducer and are 3" all the weay to the end. If you are just getting the cat-back get the kit that matches your engine code. That way it will bolt right up to your cat and you can cut off the reducer when it comes time to step up to a 3" cat.

 

I dont have a cat so how would i be able to get a reducer to go from 3" to 2.25" so i can put the cat back directly on to my car. (the cat was taken out when the headers were put in)
would an exhaust shop be able to weld everything up with the reducer in there?