Your true south satellite is the one that is closest to your longitude. In your case I would use AMC3 at 87W. It is a good satelite to use because it has few transponders that are quite strong and always on.
Check out
http://www.lyngsat.com/amc3.html to find a transponder. Since your setup is ku band, look fo rfrequencies of 11700+.
PBS Mux at 12110H 14025 SR has always been good for me.
On your motor. You should have two scales. One side hase your elevation, the other has your latitude. Just ignore the elevation one nad set the latitude one to match your latiitude 42.9.