Is glycol miscible with gasoline? If so, I would bite the bullet and replace the coolant. If not, I might be fine only removing the gasoline and the topmost inch of coolant.
I mostly concerned with not blowing up and keeping radiator
fluid away from my dog and cats. So far, I'm thinking I'll do
as Fazer suggested and drain the radiator.
The recycle part of the dump is closed down because of the virus,
so I don't think I'll have a place to take the used radiator fluid

...
My (I think) original radiator finally gave up the ghost a few years ago
and I put a $100 Chinese radiator from Amazon on there (Ford 8N),
hopefully the drain plug will do right...
-Mike