Yeah, they were an upgrade via STC. As I recall, they were a separate STC from the -1 engine upgrade (as in they're not part of that package), bit not sure they work on -43A/BL engines. I'm assuming they do. There was also an intermediate version where rather than a digital readout, you had a LED light ring (if I recall correctly).
I can't remember who makes these gauges at the top of my head, but I can check when I get the books back from annual. In them emanative, maybe someone will know on the forum.