I made a circular adapter plate out of 1/4" thick aluminum to make it fit. After bolting the aluminum plate to the existing linkage, I mounted the arm with the ball stud off the old throttle body on the adapter plate. It works great and looks neat. You will need an aircraft type countersink for one of the bolts that secures the plate to the explorer linkage arm. It ends up being under the arm with the ball stud for the linkage.
A trip to the welding shop with the explorer TB and the arm from your old Mustang TB would probably accomplish the same thing. I didn't have access to a welder, so I fabb'ed the plate in my shop. I took about 1.5 hours to do it, it was a measure, cut, and fit type of operation.