Sure.
Wire harnesses have plastic fittings at the ends to connect them to gauges, ignition switches, lights, etc. There are lots of different shapes and configurations on a given car. Of course when a new model year is released, sometimes the shape, size and configuration changes.
So when changing the lights out in your car, you can hack up the harness, use some crimp type butt splices, and wrap it all up with electrical tape.
Or, you can buy the mating connectors and wire ends for each of the year of each side, buy some appropriate wire and the proper crimping tool (you'll need a crimper that does a "W" crimp, SnapOn and MAC both sell very good quality crimpers, online, well worth the money), and make up a harness that adapts the plug on your car's harness to the connectors for the lights.
Like these:
There are many different types, do some digging and get some of what you need. They are available from a place (sorry, I can't remember, but someone here will chime in) that sells reproductions for all kinds of classic cars.
It is really easy. Get a wiring diagram for each car, find the wire in the car's harness for one light function, say, tail lights, identify what position in the connector body correlates to it, terminate the wire with the proper terminal, and slip it into the connector body (it should snap into place, and if you mess up and stick it in the wrong spot, there are tools available for reaching inside the connector and releasing the tang on the terminal). Do the same thing for that function on the tail lights.
Repeat with each function until you have all the functions covered and you have run out of wires to match up.
It's easy.
Honest.
Oh, and you'll be able to convince your wife to allow you to spend money on tools. Every man needs tools.
Don't have a wife to ask if you can buy tools?
You're doing better than me then.