3: Depends, but If your using the stock 7.5" diff, you could use the 3.58 (auto gear), the manual is a 3.42 R&P.
4: It can and does, but if you abuse it with wide sticky tires then it will eventually fail.
5: You want a front sump from an LS400.
The 8" comes in pre-tacoma v6, and a few...