So the Toybox is the best thing ever in an FJ60. I hope it comes back. I've run mine now 9 years or so and it's changed the nature of the beast. Great piece of kit.
I have this idea of building my FJ62 with an SM465/Toybox/Split case, if it's ever a thing. I have most of the parts already. That gets into the stupid low zone and honestly not needed either but fun to consider.
But it would be a serious challenge to make it work behind an 80. And really not practical. 80s work ok as they are, especially with the low range lower gear, that there almost isn't a reason to do what you want. To put it behind an 80, you'd need to get an adapter made, move the fuel tank, add a split case, delete the AWD, and do a whole bunch of other things for something you don't need. Especially when you consider it would be cheaper in the end to go domestic 5.3 LS motor/4L60e/Atlas. Plus, even though the Toybox has held up for me, I'm not sure it would survive the size, weight and power of an 80 series. It is in the end a mini-truck transfer case. At a certain power/torque level you need to rethink where you're going.
As much as I like and respect Marlin, you might be better off going the direction of the black box that can handle more torque.
You definitely could. All you would need is a 3 speed bellhousing, H42, Marlin Toybox and split case. But there's no way to get from A440/A442 to the Toybox. (Though I think it was done once!)
And @Will Van what trails are you running in Texas the require such low gears? You might be ok as is.
