i believe those lug nuts are the "bulge seat" style, similar to what is used on new[er] factory aluminum wheels.
as for thread engagement, i like to see at least 1 1/2 times the stud diameter. so for the factory size of 7/16, [.437] it would be .655. a little more wouldn't hurt, but with a closed end lug nut, you need to be sure the nut has enough thread, and is deep enough internally, so as to not bottom out on the stud before being properly torqued.
when i have doubts on something like this, [even after measuring the internal thread depth] i get an extra nut and trim the end off on the lathe, or drill through the end of the nut with a drill slightly smaller than the thread, thereby being able to see just exactly how much thread engagement i have.