Need Help Identifying Power Steering Ports

Hello! I swapped a 5.3 into my 1997 Ford F150. I'm down to the power steering hose hook ups. I'm using a 2000 Silverado PS pump. I thought I figured it out but when I filled my box, the big threaded port on the bottom was not plugged. All my fluid hit the garage floor. Can someone tell me which port is the "in"? Which is the "out" and what the third is used for?

the lower threaded port is the high pressure out put to the gear box and the lower line by the threaded port is the return line. The high port near the top is the hydroboost return port, that can be plugged off if you are not running hydraboost assist

Thanks, Ray