There were two diesel engines and (I think, but I'm not sure) two petrol engines depending on market and spec. @MITSU_MAN would be able to answer in more detail.
AFAIK, the diesels were the 2.8 4M40 and the 3.2 4M41, while the petrol were the 3.5 6G74 and the 3.8 6G75.
As far as the petrol engines are concerned, for the most part you'll find them in direct-injection.
As for the diesel engines, I'm not really sure. I think the 2.8 litre 4M40 which is still used in some markets (Pakistan included last time I heard) is still stuck on the basic spec from the mid to late '90s and is an indirect-injection type. I think over the years the injection pump changed from a mechanical to an electronic-controlled type.
The 3.2 4M41 was also proposed in two versions, both direct injection, the first one with an electronic-control distributor type injection pump and the second with the common rail direct fuel injection system.
There is one engine that has continued to live even though the 4M4x family has taken over the Pajero range, and that is the 4D56. That engine "supposedly"died with the 2nd Gen Pajero, but with a couple of redesigns and nowadays with Common Rail Direct Injection and a Variable Geometry Turbo, lives on in the L200 / Triton truck. The highest spec of this engine comes in the "Barbarian" spec L200 and punches out 175 bhp and 350-odd Nm of torque. It's almost on equal footing with the bigger and more "modern" 4M41.
I'd love to have that in an SWB Gen 1 Pajero. Add Gen 2 suspension bits and transmission, and you've got a real dirt-tearer. Assuming a 1600 kg all-up weight and 175 bhp, you're looking at around 9kg/hp weight to power ratio.
