The A340-213X aka A340-8000 which was sold to the Sultan of Brunei is the only one ever produced. Initially the A340-8000 was referred to as "A340-200HGW".
Two further -213 (without X) went to the Saudi Arabian VIP flight. (What´s the difference between the X and the non-X version?)
iirc the -8000 gains her superior by sacrificing some cargo space for additional fule tanks. For that reason the wing structure is slightly enforced where it´s joined to the hull (again, iirc).