I have had Rallye taillights in my '72 non Rallye for years, everything hooked right up, no problems.
The problem: the left taillight was bent from a wreck.
I have another light to replace it, but the harness isn't real easy to change because the sockets were not made to be removed.
What are my options-cut the harness and splice wires or...?

Splice, solder, and shrink wrap with a weather proof connector in-between. They way they made those lamps is a real pain. At least with a little work they will be easily removable in the future.