HSBC Holdings Plc has made insurance executive Mark Tucker the preferred candidate to be chairman, replacing Douglas Flint, according to two people familiar with the decision, as Europe's largest bank takes the first step to overhaul its top management team. Prudential Plc , is in discussions with the bank, according to the people who asked not to be identified because the succession process is private. Flint, 61, is expected to step down after six years as executive chairman and 21 years at the bank.