Well if someone on here knows a strong transponder on 78w im guessing that will be close to your true south satellite based on my guess work from your information you provided. if KE4EST jumps in he might be the source for helping you with your southern satellite. in the list that has strong transponders it shows 83.0 °W (AMC 9) 11840 H 26666 or 11900 V 30000 has a strong signal in the general direction of your true south. So if it were me id zero the motor, eyeball south with a compass (or use dishpointer and any reference points in the direction it shows true south) and move the dish to whatever satellite winds up being closest to your true south, and move the elevation of the dish up and down till you get a reading then peak it from there. Then once you get that as good as you can get it move the dish to the east or west twards the end of the arc and see if you can pick up one of those satellites and if you need to peak the dish some more. I was able to make a crude jig to set my compass on and affix to my motor to get my true south. Once i had elevation set i only had to bump the whole assembly a little bit to peak the signal. im still using the setup and pick up every satellite ive aimed at on the arc. Maybe i got lucky I dont know.
Well it's turning out to be a bigger job than I had anticipated. I need to look at the KE4EST document again and make sure everything is set up right. I have a hole in my motor mount but the dish isn't going through it. In fact it's just in some random position. So I need to fix that too because the furthest the dish will go down is 10 degrees, and I need to be somewhere around 5. This is proving to be a good weekend project for sure!!