Help with a measurement rear 02 location 3.4

So I have done some searching and this is probably not a thing for most.
I put a 3.4 in my 91 Ex cab Toyota and am taking it in for custom exhaust on fri.
I hacked and pulled from the donor and am un use how far back the rear O2 goes behind the cat so if one of you helpful TW members could grab me a measurement from the cat flange to the center of the rear O2 I would be greatful. Thanks

 

3.5" from face of flange to center of 02 flange. That's from an 03.

 

It really does not seem to be that critical

The back sensor just allows the ECM to see the difference between the cat or two cats if California emissions

In my 92 Swap the exhaust was welded at first it was right behind the cat I moved it back about 6" works fine no codes.

 

Copy thanks so much for the help.
I didn't think it mattered that much ether but my exhaust buddy was sure worried.
Now he can set it dead on.
THANKS again so much.
Try post some pics this weekend after I get a few more things buttoned up.