Crank shape?
 

I ride a 80's Schwinn Super Le Tour and the cranks are straight. I notice that newer cranks have a curve in them. Is there a reason for this? Does it provide for more clearance for the ankle bone?

It might, but that's not the reason. Over the years crank sets and BB's have moved to progressively shorter spindles to improve stiffness. That moved the hub (spindle end) of the crank inboard. But the pedals had to stay roughly the same width apart to clear chainrings and chainstays, so you have today's curved arms.