sounds like some good ol boys fix for the last time he lost the nuts, that slotting to make a lock nut, GM never did that and I certainly wouldn't have taken it on the highway like that
as I said above, the thing to do is check with a truck tire shop and see if they can get you the right size of the hub piloted nuts - or check
this place out that crenweige linked on a big bolt thread, might find something there, the black one bottom right looks useful
Bill
