I carefully drill-out/open up the screw holes in the new caps so they fit the old screw pattern in the wheels. Gotta' be careful though since the new plastic caps have plating that comes off easily. My wheels (seen in the post above and here) have a "special" mix silver paint sprayed on the spokes by the guy who restored them. Another TT restorer I know uses the darker gray (lower image) on the spokes--I think it's just a matter of taste and technique. Oh, and always run a tap in the screw holes and clean them up so you don't strip the center cap screws!
I'd rather look at old TTs than a beautiful woman... (Old TTs are cheaper!)