I just helped my son install a high torque starter in his 65 mustang. The starter has a post for the battery wire and another mail flat pin for a wire. Does any one know how to wire this properly? Do mwe need to remove the solenoid on the fender well and wire the battery directly and the I wire to the starter pin?
Any suggestions will help.  

You can keep the starter relay if you want but you need to get a source of voltage to the new starter's flag terminal that comes from the ign sw start circuit. If it was me, I would move all the battery cables to the battery side of the relay and then run a wire from the relay's start terminal wire to the flag terminal on the new starter.