[Chevelle-list] 64 bumper bracket nuts

[chevelle292wagon dejazzd.com]

Hi,
Anyone know where to get the nuts that slip onto the frame of a 64 to hold the 
the bumper bracket to the frame?
These resemble the "u" or "j" nuts that hold the inner fenders to the outers 
but have a 1/2"-13 thread.
Checked the major Chevelle suppliers but could not find a listing.
If only I knew I'd need them before I went to Hershey!