Depends what you are trying to do and if you want more power or stay diesel and your budget.There are many options. Here are a few that are common for swaps. Cheaper if you do it yourself but still $. Read more on Mud about below.
Gasser
Toyota 2f/ 2UZ/1FZFE
Chevy (350/LS)
Diesel
Toyota (2H, 1HZ, 3B, 13BT, 15BT, 12HT, 1HDT, 1HDTFE)
Cummins (4B, R2.8)
I have several 2H engines for sale if you go this route. You will need a new bellhousing to match engine of choice and transmission of choice. I have bellhousings for 2H and 12HT and which takes Toyota 4 and 5 speed transmissions.
LS and 1HDTFE require more complex wiring/ECUs
LS engines are getting very popular for power/$ or Hp compared to any stock Toyota engine above. It is very well designed engine and simple to work on. A die hard Toyota guy’s opinion here. Best combo for faster highway speeds and off-road needs. Advanced Adapters makes parts to bring components together for non Toyota needs.
I also have H engine parts if you need. Parts are getting hard to get though. Keep that in mind.