Will the LS1 stock y-pipe and cats from a 4th Gen fit on a 3rd Gen?

 

That is a good question, but i would have to believe the answer is no. All of the third gen conversions that i have seen have had a custom y-pipe made. Some start with 4gen y's and modify them. As far as the cats go, i believe i have seen some go in without modifications, but i have also read that some people have to have the flanges cut off and rewelded to keep from hitting the frame with the O2 sensor. It might depend on the year of the donor car as well. The cats and y-pipe changed between 99-00 year models.

Clint