I have seen a few "correct" nuts. I have tried to Xreference the original part number of the nut (it is the same for L6 and all V-8's) and is 3829086 which at AMK turns up an ordinary grade 5 3/8-16 nut.
The locking versions I've thought were correct are in these pics, my prejudiced preference is for the ordinary nut style in the first pic.
Thanks for comment please