I'm headed from Boulder down to Puebelo this Saturday to pick up my very first answer. As luck would have it there is a decent winter storm brewing in the area and it could dump 5-8" along my journey. As the car has a set of crappy all seasons, I have tracked down a cheapo set of OEM steelies w/ snow tires to get me home.
Question, when swapping between factory 7-spoke alloys to steelies on a 94 Miata, do I need special lug nuts to fit the steel wheels? It would be a bummer (to say the least) to find out the lugs won't properly seat in a cold snowy parking lot Saturday evening. Link below fore the wheel/tire set I'm going to pick up in a couple of hours.
http://denver.craigslist.org/wto/5536655789.html
Picture of the car, since I know you folks like that sort of thing.
I hate giving advice like this when actual travel plans depend on it, but IIRC, there are only 2 types of factory lug nuts available on NA Miatas an "acorn" style and a "short" style. They both seat the same way. How do I know this, you ask? The counter guy at NAPA sold me the "acorn" style when I needed the "short" style, which are used on the various BBS offerings that came with certain special edition NA's. Both seat exactly the same way, though. The "acorn" style are just taller and cover the end of the lug nut.
And now, I'll be the first of many to ask, "Is the hardtop for sale?" 
Miata lug nuts are unremarkable. As long as you're not using some weird spherical seat nut from a Porsche or Mercedes, you'll be fine. All the factory wheels use the same sort of nuts.
Awesome, thanks for the quick reply guys.
And with regards to the hard top, that was a major selling point. I think I'll keep it around for a while.
If the stock alloy wheel nuts hold the steel spare on, they'll work with any regular 60 deg. seat steel wheel (So no Honda/euro ball seat or 45 deg. race seat).
