I looked at the Pelican electrical schematics and in the electrical section of the factory workshop manual and give this information.
On page 3.3-2/2 of the WSM, there is a picture of the front turn signal with the pins and function labeled as:
Earth contact (31)
Side marker lamp contact (58)
Blinker lamp contact (49 R/L)
So I'd say 31 is ground and 58=57 is the side marker and BL is the "blinker". I can't capture a copy of the pic.
The electrical diagram wasn't much help with the terminal numbers.
http://www.pelicanparts.com/914/parts/Elec...lectric_74C.jpgIt shows connections to terminal 58 to side marker.
What year is your car? The electrical schematics are 73-76ish. If yours is an early car, maybe that's why the terminal numbers/id's are different.