Can you have the new cats welded to the old pipes? You can sell the old cats to a scrap yard--for good money.
I'm really considering doing this. But there's a couple issues with it.
The original cats in this truck are effectively gutted, leaving none of the valuable recyclable catalyst material. So it only has worth as scrap metal. They
could have been worth $400 each in a core return but since the previous owner hacked off the ends, GM won't take them. Guy on the phone at GM parts said that GM is very particular about catalytic converter core returns. If the piping with the cat has been cut or modified at all they won't take it.
I think the Engineer in me just wants the original parts so everything bolts in exactly as it would from the factory. And i know that if i don't get it back to "factory" configuration, i'll pay for it later on when something goes wrong.
So, i'll be offloading the wrong replacement catalytic converters i bought and stomaching the hit for new correct OEM cats. This will still have to wait for me to recoop some funds from selling the wrong cats i bought. So i guess if i have to move the truck it will have open headers for a little bit LOL