As far as I know the Rangers were first fitted with a 2.2L Perkins diesel producing an incredible 59hp and they then went to a 2.3 Mitsubishi turbo producing an astonshing 85hp.
I remember a thread running on the Ranger page (I think), maybe about this time last year but can`t remember much.
There is I am told a vid on You Tube of an original diesel Ranger doing a 0-60, may be worth a look.
I also saw somewhere that some guys are getting up to 28mpg out of them.