Contacted Cruz Pro regarding several issues. Their response was interesting:
"Our digital gauges all have built in user-settable low and high alarms so your existing alarm senders become redundant. You may find that you can replace the existing ON/OFF senders with proper resistive senders and screw them into the same fittings as the existing alarm senders.
To display alternator output you need to be able top place a current shunt in the negative leg of the alternator. This is easy If your alternator has a floating negative output but very difficult if your alternator negative is connected to the alternator case. The CruzPro A60 (CruzPro A30 Digital Amps Gauge
) is the only digital ammeter that we manufacture. Some of our battery monitors such as the VAH60, VAH65 and VAH110 also have a built-in ammeter function as well as the voltmeters.
The current that our LCD voltmeters draw is very low however (only about 0.035 amps) at maximum backlight intensity. Even a small 90 amp 12V battery would run the voltmeter for months."
So it seems the current draw isn't an issue. I could set an alarm on the AMP and Volt meter to alert me when the current dropped below a certain level. Seems even more fool proof than aligning the analog needles. Not clear on the "floating negative output" I think my alternator has a negative wire. Anyone know for a Yamar 2GM20?