OK, well I'm back on this as I've got my Goodyears ready to go, dropping off my wheels to be painted tomorrow, and still don't have lug nuts.
What I need are 5/8" thread, 18tpi, about 1.25" or so usable length, chrome...they may not even exist. Here's the catch. Since they're being used with a clamp ring, I'm pretty sure the conical seat is supposed to be 90 degrees.
Those lugs in the Prestige link I posted above are 60 degree. The only 90 degree dually lugs they've got are 9/16, 14mm, etc. no 5/8"