Outer Limits 4x4 Board

While I know this is not a common engine here in Australia, I'm hoping somebody here will have experiance with it. (also the reason why I've posted here instead of GM section)

Like Milo, I'm also building a tow Rig, Mine is a 1990 C2500 picku, extra cab & Long wheel base.
Lowered 8" alloys yada yada yada.

I bought it less motor and box, which brings me to my currrent question.

I've bought a Vortec 8100 which for the uneducated a 496 cube gen VII big block, loosly based on the LS series.
As far as I'm able to find out, the PCM programming is almost identical to the LS engines as well,
What I need to find out if I can disable two of the 4 oxygen sensors so I can run aftermarket headers and Cats.

I'm hoping that with a cam, exhaust, decent air intake and a mafless tune it'll make close to 500hp on normal unleaded
as the highest spec version of this engine made 425hp in a 50 states smog legal form.

Should be no reason why they can't numb rear 02 sensors when you get a tune and remap computer.all the ve and vz commodores were done once out of warranty and exhaust upgrade was done.