My understanding is that the 7.3 IDI uses the same glow plugs regardless of the vehicle they were used in. I will share some experience of a friend who has this engine in his box truck - don't replace them with cheap ones unless you want to replace them again a month later.
The correct glow plug should be the Motocraft ZD9. These should last a decade: https://amzn.to/2rvgKDi
You can also test the glow plugs with a multimeter, use the resistance setting to measure ohms between the engine block and the connector on top of the plug. You should get a reading between 2 and 6 ohms (you really want between 2 and 3 ohms though), and it should be consistent across all the plugs. If you have an outlier, it's likely failing. 0 ohms is a plug that's shorted to ground, anything higher than 6 ohms isn't going to heat up properly.