F250 HD's like the one in your Avatar (91-97) used a Dana 50. A Twin-Trac Beam version of it anyway. An F350 of this vintage would have a solid axle Dana 60. The 99-02 Super Dutys (F250/350/Excursion) used Dana 50's with the exception of the F350 dually which got a 60. The '03 and up Super Dutys used Dana 60's, while the Excursion retained the 50 until it was discontinued after the '05 model year.