Ignition on power in a 65 dart

Hi, I’m looking for ignition on power in my 65 Dart. I want to wire up some accessories and would like to add a mini fuse panel. A guy I know said run a line from the alternator guage?? Just want some advice. Thank you
You need to tell us more about what you are doing AND THE LOAD involved

The alternator gauge/ ammeter is CONSTANT power and you are saying "ignition on." IS THAT what you really mean, or do you want "accessory" power?

There is only one ultimate source of switched power---the IGNITION SWITCH

It's outputs are

ACCESSORY---hot either in "accessory" or "run" position of the key.........the wire feeds from the switch to the ACC buss in the fuse panel

"RUN"--hot ONLY in the run position. Feeds off (NOT fused) to the clusther, through the bulkhead to the VR, the ballast resistor

I WOULD NOT pull much added load of either of those two outputs. Instead, I'd used one to "fire" a relay and power the relay off a breaker/ fuse with a more direct path to the battery

There are many pitfalls IF you are going to run heavy current additions. Such examples are large stereo "amps", electric fuel or coolant pumps or electric fans, but there are certainly others.