So, I'm going to be replacing both cats after the winter, but for now I have a new Y-pipe, and a great condition used y-pipe back top speed exhaust I want to install. My question is, has anyone used a flange repair kit on the ends of the cats to the y-pipe? Where the cats meet the y-pipe is a rusted mess, it'll likely be easiest for me to sawzall off the y-pipe right after the cats and cut the bolts off, etc.

I was thinking I could mate the new ypipe to the cats using flange repair kits, with permatex orange gasket maker and the gaskets included to prevent leaks, and not try to bolt the new y-pipe to the end of the cats which are rusty and nasty. Any advice? below is a link to a sample of the flange repair kit. Also if anyone knows, what is the diameter needed for the flange repair kit for this project, if anyone knows?

 

I ask because we're really tight on cash right now and the break is right under the driver's seat. The sound is almost unbearable when going Kodi about 45mph.