Kerry's 330 GT Restoration
A while ago I bought a pair of front turn signals on ebay. These had bad lenses, but the body and chrome were in fine shape. Both of mine needed to be re-chromed and one was slightly dented. The price was quite reasonable and less than what it would have been to re-chrome mine.
The first thing to do was move my lenses and bulbs to the new units. But first I took the lenses and using the plastic polishing compound and wheel, I removed all of the scratches and imperfections. You do have to be careful as the lettering is just raised plastic and the polishing could ruin them. Here's one of the polished lenses.
The next issue is getting the plastic trim piece that fits against the car body glued to the turn signal body. Over the years, it seems that the plastic has shrunk somewhat. Since the back of the turn signal is concave, the plastic tries to go directly from corner to corner and doesn't want to stay stuck in the middle. So I used contact cement and plenty of clamps leaving them on for a couple of days to make sure that the cement was at full strength.
Finally the trim plastic was well glued and I was able to install the turn signals on the car. Here's the final result.