the answer from bongo towers is as follows, unless others know better

kerb weight is the unladen weight, in this case a 2 wheel drive aft 1770kgs, plus full tank of fuel= 65kgs, plus average driver weight = 75kg ish. it is said to add the conversion weight, but im not too sure as the removed seats must weigh approx the same ??.
i did a search this morning and found a million different answers.
anyone any additional info please.