You can use comercial available pneumatic cylinders, but they are normaly rated to 10 bar pressure. For a dozer this will be aceptable, no need for heavy lift like loader or exacavator. If you use hydraulic cylinder available, they look to bulky.
Check out on vendor pages for cylinders, like this from PMD
http://www.gardentrucking.com/produc...esort=1&max=10
Scale? Depends if you should use it together with other models, bigger = heavier = more power needed.
Dan