Thanks for the suggestions. I didn't know there was so much out there. I'm kind of leaning towards the epoxy stuff I'm finding.
I'm running out of reasons to not get that girl out again. It's been in the shed since 84. (I kind of retired it when I got my Moto Guzzis.)
Be sure to use a product that specifically mentions ethanol resistance and compatibility with fiberglass; some of them are formulated to work on old rusty steel tanks without much thought to fiberglass. Also, make sure it's intended for "slosh" application. If it's a single-stage product (like the one sold by Aircraft Spruce), you can recapture the excess and put it back in the can for additional coats. If it's a mixed binary, you only get one shot.
I'm not sure if the carbs require any updated gaskets or floats on that bike (the forums should have that info), but you definitely want to replace all the fuel line with the newer Gates line that has a green stripe. If it's a pure gravity feed, you should be okay. The biggest pain for classic car and truck owners is the lack of ethanol-friendly mechanical fuel pumps... most end up running an electric pump.