This information comes predominantly from the "Differentials" book from Randy Lyman of Randy's Ring & Pinion.
You can probably eliminate the Dana 44 pretty easily as it is a light duty axle that is not suitable for use on a 3/4 ton truck and were never installed as original equipment on anything bigger than a 1/2 ton. Another disqualifier is the 8 bolt axles - you won't find them on a Dana 44.
The Dana 50 is a front axle application only, and modifying it for use in the rear would be very expensive, complicated, and pointless (if even possible).
So out of the 3 you listed, the Dana 60 is the most likely - it was also the axle that Ford originally installed in the F-250 until 1985. I have also read that left hand thread lug nuts were used on the driver's side during that time.
There are 2 other Dana axles that might look similar to the 60 - the Dana 61 & Dana 70. The 61 was only used on 2 wheel drive F-250/F-350 & E-250/E-350 applications from the mid '70's to mid '80's. The Dana 70 was used on dually applications almost exclusively (used by Ford, Dodge, GM, International, and Jeep)
Usually the easiest way to identify an axle is by the shape and bolt count of the rear cover since any other markings on the axle are either not permanent in nature or covered by rust. There may be a tag on one of the bolts on the differential cover, but those tags usually only identify gear ratio and possibly the presence of limited slip. In the book I have, the Dana 60/61/70 cover is the same, so the only way to tell the difference between them is by gear ratio and ring gear diameter.
If you can post a picture of the cover, I'll compare it to pictures in my book, or you can find pictures of the axle covers somewhere in the vastness of the internet.
