Hey guys so I cut my exhaust completely off when I was getting my transmission out it needed an new exhaust anyways as their were too many leaks I never had any issues with the old cats other than their rusty as hell do you think I could sand them down cut the rusted bolts off and reuse them? is their any way of knowing if their good or bad and is their a way to clean the inside

 

No, no way to tell if a Cat has good flow until its on a running engine
And no way to clean them internally