Crimp those wires...
I've had problems with soldering when there's vibration involved. The wires are much more prone to breakage when they are soldered, as the individual strands cannot flex as well. For this reason I prefer to use a good crimp connector. If you are worried about possible corrosion, use some silicon and coat both ends of the crimped connection, then wrap with tape.
'82 300D/4.3L V6