lt1 catback to ls1

will a borla catback from a 97 lt1 fit my 99 ls1? or what kind of modifications would i have to do?

It might not bolt right up in your driveway. But, if you take it to a muffler shop they can do it. When I bought my loudmouth I needed an adapter kit to fit my 1997 Z but they didn't even use it....They still only charged me like $30, and welded it so I didn't get any leaks.