it is better to but the entire donor....
There is wiring and other pieces that you would prolly forget in the donor and you can part it to recoup some of the money you spent. Donor and all I spent $2300 on everything for my swap- new plugs wires timing belt 1"body lift new seals etc.. I parted the rest fo the 4runner and recouped enough money to bring it down to around 1700. How many miles are on the tundra?
And that trans will cost you a lot to use since the tcase is drivers drop you will need another adapter and crossmember to use it. It would be easier to buy a 89-95 R150F