Ammeter to Voltmeter...who does it?

I need to thank all of you for this thread. While I don't own an A Body (or any other letter Body for that matter), I do own a 1975 MB300 Class C motorhome. I've been restoring it for the past two years, and we're at the point where we can take day trips in it now. We took it out today and the ammeter pretty much stayed at +25 during our entire trip, the first time it's done that. One of the things I did was to rebuild the wiring harness, including taking the wires out of the firewall blocks and cleaning them with BarKeeper's Friend, then packing the blocks with dielectric grease and replacing the wires.

I've decided to get rid of the ammeter and replace it with a voltmeter, however my ammeter is different from your A-Body cars...it's located in a four-gauge round cluster and the needle points down. I did manage to find two different brands of voltmeters, so I'll be doing this upgrade this winter. I do have one question, though. The ammeter has a 20A circuit breaker attached to one of the posts (see picture below)...do I need to keep it, when I convert it over to the voltmeter?

Thanks again.

Fred