Dan,
I replaced the entire rear wiring harness last year and I have no regrets since. Between the 50 year old sockets, connectors and wiring, updating this made perfect sense to me and I've had trouble free brake and tail lights since.
I ordered my harness through one of the catalog companies (OPGI, Year One, Parts Place) but I can't remember which one. There was a little delay on getting it since they are custom made and I think the recession hurt the supplier pretty badly. The quality was perfect and everything was an exact replacement. I figure that the little extra money for the entire harness was well worth avoiding all of the solder and tape joints that might have been associated with just replacing parts of the harness.
Chris