? on catalytic converter

[lowesguy]

my catalytic converter is making really bad noise,lots of rattling,makes the truck sound like s_ _t!,it was replaced about 30k ago,the original one was huge compared to what they installed,whats on there now is a free flow cat,but driving on nasty roads up in the wine country has loosened its guts,right now I don't have the cash to have it replaced,so.... I was thinking of cutting it out with my sawzall,and gutting the insides then have it welded back up there,the truck is a 78 3/4 with a 3" exhaust flow-master muff, any one ever gut their Cat?
I have to have one for smog tests here,and I just passed it last month with cleaner readings than my 300E I rebuilt!