So yesterday I went and looked at an 84 3/4 ton 6.9.
I noticed the hubs are freakin huge compared to my 83 3/4 ton with the 300 6.

Is this aftermarket or did ford put heavier front axles on with the diesel?

Mines a dana 50. The one on the 6.9 should be too right? It looks like it.. Its definetly not a dana 60.....

 

Your 83 probably has a dana 44hd and the other probably has the 50. I think the 44 has 6 bolts holding the locker on

 

Most IDIs came with a Dana 50 front axle, except for some single cabs. I've got a single '88 F-250 with a D44 front; everything else I have is D50.
And yes, the D50 hubs are bigger than the D44.

Also, the D50s share a lot of parts with the D60s - most of the knuckle outward is the same of very close. Same basic diameters.