Park is mechanically connected to the shift input shaft, no fluid required to engage. When you pull the pan, check for any linkage parts in the pan before you dump it all of the way out. It may be just a broken clip, or link.
One way to check the pump and fluid is to unhook the supply line to the trans cooler at the radiator (lower fitting on trans is supply). Put a lenth of rubber hose on it,then put the hose into a clean milk jug. Start the car and watch for fluid.
PAWN SHOP FIND
RESTORATION IN 1980...
"You can have it all, my emipre of dirt. I will let you down, I will make you hurt"