With regard to alignment be careful. The ones I have are just undersize so when you fit them into the chrome ring, and tighten up, the unit can squeeze out slightly at one point and upset the alignment. I found this out at the MOT on the Roadster when one was a bit low. Examination of the unit showed that this was the reason.
To fix it I've stuck a length of soft neoprene around the inside of the chrome ring (not the outer decorative ring) and this centralises the lamp unit and stops it squeezing through in one place.
