starting problems.. tried everything HELP

[Cobras4life]

Hey guys, I'm pretty new to the site and was hoping for your help. I have a fox mustang gt 1989 and was having some starting issues. When I try to turn on the car it won't turn over instead it acts as if it drains the battery to where I can't turn it at all. I took the battery which is fairly new to test it and they said the battery was fine. So I'm assuming its not transferring enough power.. although my meter inside the dash says the battery is pretty low.. I just got the fuel pump replaced, starter selonoid replaced, alternator replaced, and ignition module replaced. A couple of people suggested that it was the ground wires.. but I only found one going from negative battery to a cast iron water pump.. didn't see any for the starter just the wires going from the starter relay to it.. any ideas?

thanks