Greetings
Re hilux the only difference between the diesel and petrol is the diff ratio. petrol is 3.9 and diesel is 4.1.
Umm more like 8/39 gearing 4.875:1 and is very low geared. Also coupled to a non-overdriven 4 Speed the ratio's are terrible for a large engine exchange unless you are into rock-hopping and the like.
The engine code is simply 'L' the first of a series of OHC diesel engines from Toyota(actually Hino make them). Later came 2L(2.4),3L(2. and 5L(3.0).