Ripsaws come in two flavors, Husky and Stihl... has to do with the way the oil hole lines up with the mount on the Ripsaw, which lubricates the Ripsaw gears. You can not mount a Stihl saw on a Ripsaw made for a Husky, or the other way around. You CAN buy that cast aluminum mounting block and swap it out, but it is pricey, and it would be cheaper to get a used saw to fit whatever block is already on it. You can get away with as little as a 50cc saw for the Ripsaw, as it takes much less power to push that blade through the cant than a chain. A 60cc saw like the Stihl MS361 is perfect, as much power as you will need. A bigger saw only makes the whole thing that much heavier, and is not really needed. On small cants, like 8 inches or less, with a new sharp blade, I don't even run the chainsaw full bore, as you can walk it down that cant almost as fast as you can walk at that thickness.