In the next two months, Cooley Dickinson Hospital's courtship of larger healthcare institutions will get specific. It's pre-nup time. After 125 years of independence, the Northampton hospital will decide which of three big players will be its partner in a changing healthcare economy. It's expected that Cooley Dickinson's board will review a proposal for a merger or sale in late November or early December. A year from now, after regulatory reviews, the hospital could ultimately be governed from Springfield, Boston or Nashville, TN. Last spring, after first considering a less far-reaching affiliation with a bigger hospital group, the hospital's leaders switched to an outright merger or sale. The finalists for that are Baystate Health Systems of Springfield, Massachusetts General Hospital in Boston and Vanguard Health Systems of Nashville. Now, CEO Craig Melin says it's time to see which one is the right fit, in a new round of talks that he said are "getting increasingly more candid ... and putting the real questions on the table."