yeah, both slip on and hub centric ones are illegal but paint them black and itll be harder to see.
also, depending how big of slip on spacer your get i would look into getting longer wheel studs but thats just me.
and if you use hub centric ones, get lock tight glue stuff that can be found at any car place like autobarn along with slip on spacers
hub spacers can be bought at wheelworx if your wanting them.
luke, remeber taking my 34 rims off my 33. they have some decent sized hub centric spacers on there to clear the brakes.
34 rims will also need spacers on a 32