UPDATE!
Currently working on new pre-cat pipes for the car. I'm using two Magnaflow 54904 cats and 2" piping. Stainless steel O2 sensor bungs and flex pipes from Vibrant Performance, plus some CNC cut flanges round off my setup. So far I only have the front half of the pipes welded up:
Left side:
Right side hanging with the O2 bung in place:
Flanges welded to my Magnaflow 94007 cat from last years build:
Both pipes in place, waiting for the squigly bits.
Tomorrow I'll cut/weld up the curvy bits to join the pipes to the main cat and voila! Good to go. I'm getting impatient, between this and the head gaskets I haven't had my car on the road in 3 weeks.