I've been using widebands for a few years.
We just need to weld a bung somewhere into our downpipe (oops, no turbo here -maybe in the x-over pipe.). I believe that we have been using an M12 x 1.25 nut welded over an appropriately sized hole. That way it's also easy to plug up when not tuning.

I've roadtuned cars (2 x Nissan Silvias) that have used Halmeter A/F meters connected to a wideband O2 sensor. Very accurate and easy to see when dodging obstacles while simultaneously turning knobs on the MAF signal adjuster.

I was into the dash last night (considering cutting it apart to make a double DIN opening -need to find donor (small) vents first), and considered cracking open my ECU. I find it hard to believe that it is a proprietary Isuzu unit. I'll bet a dollar to a dogturd that it's a GM product, likely for a 4.3L with a little adjustment for the DOHC configuration of our motor.
Has anyone even tried using a Hypertech PP on it? My Actron works fine, but it's OBD II protocol and that's to be expected.

Three XR4Ti s!!
That sounds like a donor yard for an RS200 clone project. Might be fun!