I have an rc350. Im not looking to swap the ring and pinon on my car, but if the options out there. I may consider it.I was recently plugging transmissions into a calculator to help identify a potential swap for my mr2 when I stumbled over these.
(Ignore the top 4 transmissions, different project and tire size)
(My calculator is set to 3k rpm and takes tire size /sidewall ratio into account. For this case, its 265/35 r19)

I have the aa81e transmission with the 3.133 final drive. I imagine ita easy to swap the ring and pinon with a 4.1 from an rc250 or a 4.398 from an rx350. As the axles plugg into the lsd. All we need to verify is bolt patter and spacing and thrust. Iv never done something like this. Has anyone else?

As you can see, our transmission with the 4.398 is remarkably close to the fwd 8 speed transmission ratios that toyota makes witch makes sense as both those transmission have an option for a 4.398 from factory. (F35 and F45 like the camry)