I have the same magnaflow too and love it, you can usually get a used one on ebay or cragislist. I wanted a valid warranty so I got it here. Magnaflow 36766. Also some of the forum sponsors selling magnaflow usually have a sale going on. Either way its a great cat, sounds great, and very easy to install.
MAC pro dumps with long tube headers FTGDMFW! :rockon mine sounded sick, well it still does I just gonna finish putting together the 342 My 03 GT is getting most of the loving now sadly because the 86 is back home
I avoid welding exhaust pieces when ever possible. Obviously for fabrication and speciality pieces you have no choice but for mufflers etc, you do have a choice. Every piece of exhaust I have ever had fail has been at or near a weld either from the factory or done after. The welding removes any protective coating in the area and does not have a protective coating itself and rusts through quickly.