LCE Exhaust upgrade fitment

Y'all, I'm thinking about replacing my exhaust with these components from LCE. I'll get to the why in a minute. I want to know your opinions, will this fit?

This header:
https://www.lceperformance.com/LCE-Street-Header-Kit-3RZ-1995-2004-Single-Cat-O-p/1041054.htm

This test pipe:
https://www.lceperformance.com/Test-Pipe-3RZ-17-5-x-2-50-Flange-p/1043056.htm

And this cat-back:
https://www.lceperformance.com/Pro-Flow-Exhaust-System-3RZ-Tacoma-1995-2004-p/1042023.htm

Why? Just because really, aesthetics I guess. I have no delusions about less than cost effective power gains. My 2003 Xtracab came with the 2 cat configuration, but when I got it, the 2nd cat was deleted and the downstream O2 sensor is just hanging there not plugged in. The first cat might be bad, I really don't know how to tell. Also, I'm getting the P0135 code for the upstream O2/A/F Sensor. I ordered a replacement Denso and its on the way. I'm not getting a code for the downstream sensor, so I assume the ECU doesn't care. It doesn't affect A/F ratios anyway right?

So I could just replace the upstream sensor and leave what I have, but its janky. See pics. I was going to replace the whole exhaust with all OEM, but then I figured why not splurge on fancy stuff when it won't cost all that much more? I have a few projects going on with it right now with the frame repair/replacement. I figured while i have the back-end disassembled it would be a prime opportunity to swap out the exhaust while I'm at it.

The selected header is designed to fit the earlier single cat trucks and comes with an upstream sensor port. But I figure if I install it, attach the test pipe in lieu of the cat, and finish it off with the cat-back system, it would all line up and fit proper with no welding, is that correct? The cat-back says its got a long tube that needs to be cut to fit and should be compatible with all configurations. The pieces connect with clamps. Does anyone foresee a problem with this? Disclaimer: My state don't care about emissions. I'm also going to delete the EGR.

Pics of my current exhaust:

 

I wonder do you have something that sends a fake signal to the ECM you should have aPO420 code.

No emission test where you live?

I have found mixing exhaust manufactures gets real interesting .

one pipe is 2" to long the next is 2" to short the complete system fits just fine.

As long as you can adjust and fabricate your exhaust you can make it work.

I decided to use Walker Exhaust 30 years ago and be done.

 

I don't know why I'm not getting a P0420. There's no bung for the downstream and its just hanging there. Not sure if the electrical connection is plugged in or not. I should check. I'm wondering if the P0420 would pop up after fixing the P0135. We'll see. Who's Walker Exhaust?

 

And no, no emissions tests in my state. I could drive a nuclear powered toaster if I wanted and the state wouldn't care as long as I paid my taxes.

 

Walker Exhaust is one of the Major Exhaust system manufactures.

Exhaust parts and related accessories gaskets, hangers, clamps etc.