The frames and suspensions are the same from a 71 Chevelle and a 71 LeMans so, yes, with the 71 Chevelle headers it will fit. The PS hoses from a Chevelle should work. As has been said the starter and fuel lines are on the opposite side, so some creative extensions will be needed and the battery is located on the right in a Chevelle too. Not sure if a Chevelle battery tray will bolt right on the core support/inner fender, but it may. Here's a couple pics of a 70 Chevelle engine bay with big block stands for reference.
