7.4 vortec sending unit + electronic gauge...?

[Rede]

I've got my truck to the point where it starts (not tuned at all and not ready for a road test at all) but I noticed that I'm not seeing any movement on my oil presure gauge.

The factory oil presure sending unit on engine (7.4L out of a K2500, carbed) has a single connector just like the factory 1979 cluster I have.
I connectred them together when wiring the tach and such, but I don't seem to have any movement.


I've done a pile of google searching for the past hour, but all I seem to find is mechanical gauge setups.



Am I missing thinging vital, or are they just not compatible at all...???