You can get a YS .63 that will run circles around the .70 ultimate any day of the week. I would not go out of my way to purchase an OS that is on the way out. From past history with discontinued OS were parts are non esistant about a year later. Then you have a nice paper weight.
Try to get parts for the pump or regulater. You cannot without buying the complete assemblies. Look how OS discontiuned the best carb they ever made (OS 7D) as fast as the 1.08 was discontinued. Parts are allready limited stock and that engine is still very popular. Atleast you can get parts for a YS that is 10 years old, and a cheaper price than you will ever buy anthing for a OS.[X(]