Last year I started replacing the gauges in the Sonic. This included the alt, fuel, fuel pressure, oil pressure and water temp. I have three more open slots that I need to fill and was thinking water pressure and oil temp but have no clue on the 3rd slot. In addition to the three slots, I was also thinking of replacing the hour meter just to get all the 3" gauges the same. Thoughts?

I have a speedometer, tach and stereo control in 5" gauges and will not be replacing these (yet).
Thanks

Vacume

Vacuum is kind of nice to have if you need to fill a spot.
Oil temp and water psi are a "must have" in my opinion.
I'm assuming you "ALT" is a voltmeter.

Afr is nice

Depth

BOOST !!!

Thanks guys!!
I have a depth
Alt = voltage, yes
I think I have the AFR pigtails on the headers but was told I needed a computer to make them work (which I don't have).
I'll have to investigate the vacuum.

The gague and electronics for afr about $150 i think, much better choice than vacume.

Depth finder is a good one if you don't have one somewhere else.

Gotta make sure the WB O2 sensor will not see any water spray in the headers, those sensors dont last long if they get wet. Other than that, having a WB O2 is super nice to have, especially if you're running forced induction (where ARF is more critical).