How to get into the trunk of a 65 Barracuda????

Ok, you've seen one latch. There is another one most likely equidistant from the other edge. I'd try a putty knife jimmied up into the gap angled in to catch the anhked part of the pawl. Or put some sort of thin pry bar into the gap and pry the top of the plywood panel down toward the trunk floor. It may only be engaged by an eighth inch of so.