GM 1 wire alt on a 273?

mopar340dave's Allpar link has great info.

I would keep your current voltage regulator (instead of later flatback), and wire as mopar340dave did (ground one field wire). You may already have the later electronic regulator that looks just like the original mechanical one. If not, they should still be available. That will give you continuous electronic regulation. It should work as well as the flatback regulator, without any wiring changes. The electronic ones are potted, instead of the removable metal cover.