Grounded Tach Wire Creates a Gremlin?

That VR you have is the OEM style, i think as scody mentioned, you need to change to the "triangle" plug style for 70 and up(I think)
I gotta get with my buddy Bob who set up the dizzy with Pertronix, he handed me that VR and said wire everything factory. Hell now im questioning if Im 100% positive the gauge was in fact steady while running before the tach wire snafu. Im going with 99% lol. Or maybe 67%.