You only need the rear upper shock mount if you have the load-levelling suspension that comes with the Trailer Package and change to regular shocks.
Depending on mileage, you can get away with stock shocks, rears are easy to replace later, but you might as well do the fronts while the suspension is out, and then you can save the shock/spring assembled if you want to put it back to stock... I was planning on keeping the stock fronts, as they had only 45 000 miles on them, but had to replace them, as one was blown already!
I'm running 265/50/20 Nitto NT420 tires on 20x9.5 wheels. It is a stock size, but the tire's design and wider wheel make them look wider. As long as the outside diameter of the tires are within a few tenths of an inch, speedometer readinds are not noticeaby affected. A tuner such as a Diablosport InTune will let you ajust the system to a different size if required...
Here is what the truck looked like when I started with 18's and stock suspension...
Here is a link to a site that lets you compare tire sizes: https://www.tacomaworld.com/tirecalc
Good luck with your project!