You dont model the bricks like a 1x1.heres steps do get the dimensions
1.Open up notepad
2.Type 1 1 3 (1st one is length,second one is width,third is height(measured in thirds of one height.)
3.Press file - save as - mybrick.blb
You need a .blb file for the dimensions.then you use that file in the code.Just look at another brick code and you will understand.(You need the .blb file in the zip for it to work.)If you don't understand this for the dimensions,ask a more expierenced scripter.