I know it's not a huge jump in from the 1fz-fe to the 2uz. I also have an 01 sequoia with the 4.7. Drastically different to drive. Way more power and much better mpg. Pulled a 21 ft boat for yrs with it, no problems. No way I would pull that boat with the 1fz-fe. I actually spent a bunch of time porting, polishing and blending the intake and exhaust on the 1fz-fe head. I got my 96 from original owner with blown headgasket. Rebuilt it with oem .020 over kit and even did crower stage 1 cams. Worst decision ever. Doesn't seem to run any better than a stock 1fz-fe imo. The 4.7 is a peppy little motor that has better power and is readily available. I totally thought about a 5.3 with a 4l80 or 6l80. Tuning and stand alone is very easy. At that point why not use an atlas. Part time, lower gearing, and basically for the cost of the adapter.2uz takes up a lot more engine space since its dohc. Also you only gain about 30hp with a 2uz compared to a 1fz. I thought about putting a turbo on a 1fz rather than going LS, but then you still have about 12mpg. With the LS I have infinite options when it comes to uprading the motor and close to 20mpg. Marks offroad adapters-although made in australia-are not hard to get. I think if you want to make adapters for the 80 for which their would be some of a demand, I would consider a adapter for the 1fz auto trans to a atlas tcase or fj60 split case tcase. I think that would sell fairly well if not really well so that 1fz guys have lower tcase gearing. The stock tcase in a 80 right now can only be upgraded to 3:1 gearing, which many don't find low enough. And dual cases can't fit because of the fuel tank location.
What motor/drive train setup you running?