By Miguel Gutierrez and Dave Graham MEXICO CITY (Reuters) – Mexico's Congress was on Thursday poised to complete approval of the biggest overhaul of its oil industry since nationalization 75 years ago, opening the door to investment by oil majors in a bid to reverse falling output. The energy bill is a cornerstone of an ambitious reform agenda spanning telecoms to bank lending that President Enrique Pena Nieto hopes will boost growth in Latin America's No. 2 economy, which for years has lagged regional peers. It aims to entice companies like Exxon Mobil Corp and BP Plc to operate independently in Mexico, or partner state oil giant Pemex through production- and profit-sharing, service contracts and licenses. Lawmakers in the lower house gave general approval to the bill late on Wednesday, and then began an overnight debate of its details.