Speedhut speedo wiring

[69SCSS]

Hey guys, I put a new set of gauges in my truck, and I'm having a weird issue with the speedo, and I wanted to double check the wiring. I have a 700R4 with VSS, with a black / purple wiring pigtail. Here is how I have it wired:

Purple - signal to speedo
Black - Ground to speedo

I am assuming from the pigtail that purple is the "high" side, and black is the "low" side. The speedhut wiring says to use the signal for the white lead and ground from the sender (or chassis ground) for the black.

Why am I asking? Because right now the speedo does this: https://drive.google.com/folderview?...EE&usp=sharing

As you can see, the speedo is working OK, but the odometer is rolling about a mile every second. Over about 50mph the needle bounces like crazy. I have calibrated it a few times now, and no change. I am assuming the gauge is bad, I just want to make sure the wiring part is correct. I've been talking with Speedhut since thursday about this.

Anyone wire up a Speedhut speedo?