Fuel tank has two halves, with the fuel pump moving fuel between them, as well as supplying the engine, one half is I believe a different size to the other. This is why if you replace the fuel pump incorrectly you can run out fuel even though the fuel gauge still says 1/4 tank left. The more fuel in the tank, then there will be more on one side than the other.

This ebay auction by our forum sponsor shows a picture of the D2 tank.
https://www.ebay.co.uk/itm/132306791545