Which lug nut style for Coy's C-5?

[all4gss]

Actually I'm planning to go with the C-55's but I'm not sure which style lug nut I need.

I've got a 1980 Caballero so it's the 7/16ths - 20 thread. I rarely find these in stock but at a local swap meet a guy was selling all sizes of new lugnuts for $15 so I thought I'd pick them up ahead of time. Which style do I need?

Acorn conical seat
Acorn conical seat w/ bulge
other?

Also, all of the packages said "for steel wheels". Are there different lug nuts for aluminum (i assume the Coys are aluminum right?) wheels?

TIA

 

[mkiiisupra]

Acorn Conical Seat sir. Have them on my regal.