Without doubt a fresh 3S-GE would be the easiest. With some mild work you could be looking at around 125Kw or so.
Next easiest is a late model 3S-GE.
Easiest turbo motor by far is the 3S-GTE but you are probably looking at around $4K+ inc the engine for the swap. Might be better to flog off the ST162 for around $2K-$3K and put your $4K cash together and buy a ST165 GT4 like this one: