Regarding the badges on the horn caps, I think there should be a GM part number on the back of the badge itself if its original whereas the repro ones are plain on the back. If you remove the light coloured plastic backing from the horn cap you may be able to very gently pry the badge out of the recessed section it sits in to see if it has a GM part number on it. I bought an SS horn cap at Ballarat swap this year and was told it was original but upon inspecting the back of the badge me thinks its a repro!