The parts manuals indicate there must be a difference between 102 and 106 wheels, as they have different parts numbers (see pages below).
However, the wheels have the same 5 x 4-1/2" bolt pattern and are generally considered to be interchangeable.
While I cannot recall which is which and use them interchangeably I have been told (and have noticed) that one model has "D" shaped holes, and the other oblong holes. Work just as well, one or other. In Washington it is now illegal to use lead weights to balance tires. The studs and washers have always worked, but most tire balancers are not used to them. What is nice with Michelin 165x400 tires is that they last so very long once they are balanced
The biggest difference is in the pattern of the wheel centre.
The centre of 2000 wheels do have a star shaped pattern and the 2600 wheels do have a more flattened centre shape.
The described hole shape sounds more like the shape of the 750- and 101-series wheels. Fergat wheels have the fish mouth holes Ans the steel Borrani wheels do have oval holes.