Ok...the position SENDER (not a switch) is a variable resistor using two leads. The 'block' you referenced is just a connection method and not essential. One wire goes to the system ground and the other is the input to the gauge.
The gauge has three essential connections: a switched +12VDC, the system ground, and the Sender input. regarding colors, there wasn't an industry standard being used at that time. typically, white was used for the +12VDC (from the ignition switch), black for the ground, and the sender wire is not clearly identified in the factory manual. I vaguely remember that there was a separate (from the engine wiring harness) power trim harness used at that time. Pretty sure the power trim control wires were in it but I can't remember is the sender wire was included or not.
It shouldn't be too hard to figure out what wire goes where. If you can't find a wire needed, you can always add it. If you have 'left overs' its wise to tape them back onto the harness they emerge from.
If there is a cover on the trim motor, there should be a schematic on the 'inside' of it...that may be of some help as well.