First, all light bulb numbers for your car are located in your owner's manual. Second, most if not all lamps used in Mercedes' are Osram Sylvania. What Mercedes used in their European products may not be applicable to your car.
The correct bulb number for any car is available from the Sylvania Website using the automotive bulb locater at www.sylvania.com.
Your 1987 300E uses a # 7528 dual filiment lamp for front parking and turn signal lights.
Incidentally, you can't have a bulb as bright as your headlamps, because having a lamp in this application exceeding a brightness of 5 candlepower is illegal in California. I personally hate white/clear front parking lamps and turn signals and think they should also be illegal...
"We drive into the future using only our rearview mirror."
- Marshall McLuhan -
Northern California Wine Country...
"Turbos whistle, grapes wine..."