Park/Turn signal lamps

[mobenz]

I have a 1978 300CD which had a broken right front turn signal housing. I have ordered two replacements, one from a salvage yard, and one an aftermarket unit from a non-MB vendor. Both have the same round, two terminal bulb socket. Problem is, mine is more of an oval socket with 3 connectors. Any suggestions, other than going to the dealer and giving up the familiy inheritance for a new one?

Thanks,

Bud