Len,
Thanks for the response- I see your posts everywhere. As it turns out the 3AD1 engine was made by Isuzu for Iseki and the parts are plentiful through either Massey Ferguson or Isuzu. The parts through Isuzu are less expensive. Regarding breaking cranks- I respectfully disagree. Isuzu does not produce defective engines - at least from what I have expereinced.
As I am a bit a gear head, I am amazed at the lack of aftermarket parts for japanese made tractors (50 Hp or less) that are branded by others (MS, JD, New Holland, etc.). Tractor parts make MOPAR parts look cheap.