Yes you can as many people have done it as the Toyota diesel engines models: 1L, 2L & 2LT engines were standard in the Canada versions of the pickup and 4-Runner.
Rad below for complete info:
I have an updated article below containing more Japanese importers of diesel engines & complete vehicles:
The way the price of gasoline (petrol for Australians) is going I suggest that everyone convert their Toyotas to diesel as they are more:
fuel efficient
higher torque
waterproof
simpler
reliable
safer
can idle all day long
less overheat episodes
can burn bio diesel or vegetable oil (without glycerin)
Well to help everyone dismiss the myth that Toyota diesel pickups & SUV's are rare in USA & Canada I have included below a list of very resourcefull links that contain places to buy diesel engines/parts and complete rigs.
Toyota diesel engines models: 2L's, 2L-T's, 3L's and 5L