It looks like your car is a '64, so the switch over will be legal (unlike my late 230, which has illegal all red lights and which has failed one MOT as a result).
I got my complete set of rear lights from Kienle, which are a world class outfit, who - unsurprisingly - charge world class outfit prices. I was able to use mates rates to reduce the cost of a full set of OEM lights with surrounds, gaskets, etc, but there were still not far off 800 euros.
http://www.kienle.com/index.cgi?lang=en I'm sure they'd be glad to help.
Have a good search on the site. Lots has been written about rear lights. Alfred (66 and Blue) will be able to add some helpful advice, I'm sure, as can others.
I recently put LEDs into my all red rear lights to improve the vis at night. Made a huge difference.