Itneresting thread. Kind of rare to hear about bolts flying apart inside a differential. Obviously defective bolts. At least you got lucky since the bolt head didn't get stuck in the ring and pinion hypoid gear teeth while you were moving. Edit: I had an old 88 ford E150 van years ago, LSD differential. I was using to tow a junk car out of the mud, one of the tabs broke on the LSD clutch pack, that tab got stuck in the gears while moving and it broke the carrier, not the gears. Fixable (new carrier and clutch pack) but it was expensive.
I'd be curious to know if for example those bolt heads would snap off under the correct torque specs. Can you test that one good bolt you have? Do a destructive test? thread it into a nut and torque it to normal specs, then increase the torque in 10 lb increments to see how much it takes to snap it off. Then compare that to a good new grade 8.
IF im not mistaken, the 98 auto 12v trucks got the dana 70, correct?