On my 73 I've noticed that recently the ammeter bounces around a lot. Usually happens when I have the lights and/or fan running (ie. more load), but there are also times when the needle is rock solid in the center with them on, and then when I turn them off it starts bouncing. I cannot find a consistent cause and effect for this.

I saw this thread:

http://www.classiczcars.com/forums/showthread.php?s=&threadid=1868&highlight=ammeter

and last weekend thought I would open up the voltage regulator and clean the contacts. But the PO had swapped it for a solid state unit. I opened it up and all looks well, and the connectors all look to be making a good connection.

Any suggestions besides replacing the VR?

I'd forgotten about that post. It's your VR. Replace it and your bouncing meter is no more.

I put a new one in tonight and the needle is steady now. Definitely one of the easier (and cheaper) fixes so far... :classic:

You bet! Most of the electronics are 30 yrs old. I started to replace most of the relays and other electical components as a preventative measure.