I think it would have to be the drive belt pulley cover.
what I did to it was sand the paint off completely, then I took a 5″ hole saw and begun to remove the part of the cover I did not need , than I had a friend of mine Cnc cut a piece of. 125 aluminium sheet about 6″×6″ logo of a german cross ,I than proceeded to fit and weld it back on the pulley cover, than I took a piece of stainless steel perforated sheet cut it to the size I needed than used JB weld steel putty and press it around the inside of the pulley cover making sure I didn’t have any putty expose so it would not be seen on the outside. after everything cured I went ahead and polished it with aluminum rouge polish.
the small details on the bike . Brass bolts , some of the parts of the bike are sanded down to mill finish, then I took scotch brite pad and brushed the parts back and forth in the same direction giving that brushed look effect. finished it off with satin clear coat .
I get alot of compliments on it .especially at the traffic light. I live in Jacksonville, FL. and I have not seen a sportster converted into a cafe racer yet.