Questions about gauges

[Fast stang16]

The other day when I was putting in some reverse glow gauges I noticed that the owner had put cobra gauges in my car (I was thinking they were just white face plates) my question is, is that the rpm readings aren't the same so which one is right? According to the cobra gauges when it says I'm running 3k the underglow gt overlays say I'm running 2500?

 

[Fast stang16]

Info in in sig.


1994 5.0 forged internals, 12:1 Pistons, x303 cam, edelbrock upper and lower intake, trickflow heads, 70mm throttle body, 1.6 rockers, msd ignition, 24lb injectors, underdrive pulleys, bassani exhaust, 4.10 gears, 5 speed

 

[lutter94]

It's possible the PO put a cobra instrument cluster. IT probably also has a 160 mph speedo? If it does have the cobra cluster, you're going to have issues with your new overlays. Only thing you can do is to swap a GT cluster back into it, or get different overlays......

 

[red94]

I have never trusted the factory tach. Ive seen cars off as much as 800+ rpms when setting the idle with a dwell. While im not a fan of the huge aftermarket tachs, I always have one run from the msd in any car im going to have near redline frquently.