How do you define relatively simple?
The 1VD (4.5 V8 diesel) is turbocharged (variable geometry) and common rail, and is probably happier on better diesel (my old H will run on cooking oil at a push). They are not infallible, and are becoming notorious for dusting up and also being hard to work on (I believe the starter or alternator is buried in the valley for packaging purposes...)
If you want an Africa-spec one, then you'll get a
1HZ from Toyota Gibraltar, or in South Africa a 1HZ, 1VD or 1GR-FE - and that's as close to simple as you'll get.