I found a set of steelies w/Blizzaks, which seem to fit great: bolt pattern & bore are spot on, and I have zero rubbing or noise indicating a problem. Thing is, the hub protrudes about 6 mm beyond the rim's outer surface, and I don't know if this is normal. Again, no indication of rubbing or binding the brakes. (tested while jacked, as well as driving, turning, braking...)

Couldn't find any direct answers in previous posts; do you pro's see this as normal, or could I need to use spacers?

 

Well I'm not a pro but I think your fine. No spacers required.

I believe the stock hub protrusion is about 12 to 14 mm and with a steel wheel your noticing this because of the thickness of the wheel when mounted.
Or another way to say it is the lack of metal, think thickness, to hide it like there was when using an alloy wheel.

Hope this helps...