just looking at the shots, and wondering if the other ones left were still tight. In the first photo,is the hub look a bit discolored or is it not washed or maybe a little heat.the second photo the stud at 8 o'clock looks to have been broken 1st. If the bearings checked out good maybe try to mount a dial indicator to the end of the axle tube (where the adjuster nut is) and check if any or how much runout there is in the face of the hub with the other studs out when you spin the wheel (hub) should even be able to leave the wheel on (bloody heavy buggers) hope its of some help other wise i agree it's the brute hp of the sv ford, maybe got a 4.00"merc crank in her