The side marker lights on the Type 34 (and the Notchback and Squareback) were originally designed as parking lights, intended for when your car was parked on the side of the road and you wanted others to know that you were there. You simply used the turn indicator lever to light up the side of the street you were on. Now, 50 years later, very few Type 34 drivers make use of this feature.
For added visibility in modern traffic you may want to consider making these side markers function as turn signals instead. Some Type 34s intended for Italy and other markets were wired this way from the factory. Once converted, the side lights will blink in tandem with the front and rear signals, as they do on many modern cars. The process is simple and can be done at home in only a matter of minutes.
First, look up under the dash at the steering column, and notice the grouping of wires connected to the column. There should be six wires. The wires connected to the L terminal (black with white stripes) and Pl terminal (white with black stripes) are for the left side turn signal and side marker, respectively. The wires connected to the R terminal (black with green stripes) and Pr terminal (white with red stripes) are for the right side turn signal and side marker.
Using female to double male adapters, join the white/black wire to the black/white wire at the L terminal, and join the white/red wire to the black/green wire at the R terminal. That's all there is to it.
– Jens Vagelpohl