The ground pins on each header is exactly the information I am looking for. TIA
The 2 pins, top and bottom, furthest right and left of each 40 pin connector are grounds. This gives you (4) grounds for each 40 pin header.
Inputs are numbered as follows (where G=GND):
Header 1:
G 2, 4, 6...32, 34, 36 G
G 1, 3, 5...31, 33, 35 G
and
Header 2:
G 38, 40, 42...68, 70, 72 G
G 37, 39, 41...67, 69, 71 G