Dan Gilbert doesn’t give up, you gotta give him that. Whether or not that’ll be enough for David Stern to look into this seriously, though, is up for debate: “The Cleveland Cavaliers have poured hundreds of thousands of dollars into a high-powered Midwestern law firm to investigate their suspicions that the Miami Heat broke NBA tampering rules while pursuing LeBron James, and owner Dan Gilbert has privately vowed he won’t relent until he has a thick binder of findings to drop on the desk of the NBA commissioner, league sources told Yahoo! Sports. The NBA won’t launch an investigation into a tampering case without a formal request from a team, but sources say Gilbert’s plan is to give commissioner David Stern a detailed case that includes meetings, phone calls and contingency plans that date as far back as 2008. Gilbert will implore Stern to use his powers as commissioner to get access to phone records and testimony of key people surrounding Heat president Pat Riley, James and others potentially involved. Gilbert will spare no expense to uncover whatever evidence he can to take to the league office, two sources with direct knowledge of the probe said. The law firm staff includes several former prosecutors with backgrounds in investigating and constructing cases, sources said.