I was wondering why Irwin made a Citation 39 and a Irwin 40 Mk II the exact same stats? The interior's are different however they seem to overlap in production years. I may be wrong on all stats but what I see seem to be the same. What was the purpose of the Mk II interior changes? I am purchasing a Mk II and was wondering how many were made as I hardly ever see any information about them. What are the weak areas to look for in a Mk II of the 1980's?