When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I think they are supposed to bolt up to the factory y pipe. FWIW I had a set, 20 years ago, on a ford truck 351 engine. They never would seal and they cracked. Hopefully you will have better luck.