Hey folks. I've got an 04 4Runner v8 4WD @ 210k miles. I have a cracked manifold (typical cold start ticking), and it's possible a manifold cat is going bad (P0430 code).

I want to get a new exhaust, if not for a bit more power, but to solve any issues that could arise from dying cats or a cracked manifold. After a fair bit of research this is what I came up with for my new exhaust system. I also am putting in a K&N intake 77-9022KP.

Edit: I have updated my parts list to be current as of 6/11/20

PARTS LIST

HEADERS - Doug Thorley THY-564-SS-C Short Tube Headers
UNIVERSAL CATS - QTY 2 - G-Sport #50025
Y-PIPE / REAR CAT - MagnaFlow #93655
CAT-BACK - MagnaFlow #15781 & Vibrant 1141 Resonator
AIR/FUEL RATIO SENSOR - QTY 2 - UPSTREAM - Denso 234-4138
OXYGEN SENSOR - DOWNSTREAM LEFT - Denso 234-4261
OXYGEN SENSOR - DOWNSTREAM RIGHT - Denso 234-4260
MANIFOLD GASKET - QTY 2 - OEM 1717350021
HEADER BOLT KIT - Stage 8 (8919) 10mm Header Bolt Kit

Questions I have..

1. I am unsure if those universal cats can be welded onto the DT headers. They do say they're for "rear". Can they be used as manifold cats, though? The DT's are meant to be welded to the factory cats, so I am wondering if this means I would need to buy the full manifold catalytic converters only to cut off the manifold part?

Edit: I ended up going with the same cats JONBOY345 used: G-Sport #50025

2. Does my vehicle have (2) cats in the rear or (1)? I am pretty sure I have only (1) cat in the rear, as this isn't/wasn't a California car. I recently read that apparently some 4Runners have (2) cats in the rear. It's confusing because I need the (4) total O2 sensors.. or so that is my understanding.

Edit: I have only (1) cat in the rear! See this Walker exhaust diagram that Ed_C posted.

3. Is there any other element of the exhaust system I may be missing? Except for the Y-Pipe, that would still be OEM I assume. I will be taking all the parts to my mechanic who is enlisting the help of his guy who does exhaust. My underbelly has surface rust, as it's been an east coast car it's entire life. Should I provide new nuts/hardware/gaskets? I am really not sure what all is needed because I have limited knowledge when it comes to exhaust systems.

Edit: Yes, there is a "front pipe" that connects from the drivers side cat to the Y-Pipe. I also added OEM Manifold Gaskets and a Stage 8 (8919) 10mm Header Bolt Kit to the parts list.

I would really appreciate any info or advice for my situation