Ammeter or voltmeter?

I'm in the process of rewiring my 73 Dart for track use only. The car has the original dash and working ammeter still installed and but I'm thinking a voltmeter may be more useful at the track. Thoughts?
Thanks,
Bill
I use a digital voltmeter in the rear bumper of my dart and a Autometer voltmeter in the dash.
The digital helps with knowing the exact state of charge where those decimal points matter.