Probably the basic starter change Ford made in the late '80s or so. All earlier starters are magnetized by the power that pulls starter up, under the side cover bump is a moveable pole that swings in a switch as that pole magnetizes and pulls in. The starter is direct drive with one shaft that goes completely through to also drive the flywheel. It uses a separate solenoid mounted up on the fender or firewall somewhere.
Later ones are permanent magnet that need no power to magnet and have a separate solenoid mounted on the side, you don't need the fender one any more. They are also gear reduction types with a planetary, not direct drive, the main drive is split into two shafts. The PMGR type (Permanent Magnet Gear Reduction), they are smaller, lighter and pack a lot of torque.
Thinking they interchange except for the solenoid issue, cables and wiring have to be run different for it. I have two Tempos, one later than the other, they both have one of each those type starters. My Pinto has the earlier direct drive one.
You can tell the difference looking at the part. Early one has a BUMP on the side, the later PMGR has a CYLINDER (the solenoid). The cylinder attaches to the front casting. Similar to a Chevy starter.