Pick up a current indicator off ebay or NAPA. These lay across the wire and show you how much current the alt. is generating (load matching). I have a set of these from Snap-on, don't waste money on the digital ones that may or may not work three years from now when you need to check it again. My Snap-on's have always worked when I needed them over the past 20yrs unlike the 6 DVMs I've been through.
(My Simpson 260M still works like a charm as well)
How big is your alternator? 10ga is not big enough for anything above 60A.
Although the voltmeter is more critical with today's electronic stuff like ignitions it doesn't really replace the amp meter. (ideally you'd want both in my view)