Here is the completed Biggie Smalls the Train train with attached wooden wheels and everything. Oliver actually found the toy quite amusing, saying "car" when he say it.
I have two new goals regarding this toy. I want to 1) make a Totoro cat bus version and 2) create one that will fit on a wooden railway set (you know, the Brio kind). I've measured those tracks out and the distance between track grooves is 20mm (about 0.8"). I don't think this 2" block will fit properly nor will its weight distribute well without doing some wood routing on the inside to store the wheel mechanism (which I don't have the tools to do). So I'll need to figure something out with the 1" blocks or need to purchase 0.75" blocks to make the trains.