'96 F250 4x4 XL Auto 5.8L (really a '97, but that adds confusion all-around)

No A/C, has PS, PB, no idea what alternator it has.

Any on-line parts source list a myriad of accessory combinations, but mostly it changes with alternator-output.

Does anyone have the proper belt # for my truck at hand?

 

I understand . Based on your post you are getting different part numbers for your truck online. Unless someone answers with a positive # . This is what I have done this to get the right one at times .
Say your belt measure's 93.500 / 93.750 . One belt listed for a 96 f250 w/351 is a Goodyear gatorback #4060935 measures 93.500, I would say this is your belt. You get the idea.

This helps with the confusion you mention. It seems from your saying you really want to order on line. If so,you must give or pick the part number. Or you could simply go to a parts store. If they are not correct,, you can take it back.
Hope this helps