It sounds like you're in pretty good shape, as long as there hasn't been enough cell plate damage to seriously compromise the current capacity of the battery. If the cell covers don't open up easily, it's possible there's some type of oddball electrolyte mix that can't be checked with a hydrometer anyway, so just give it a 15-second cranking check with the ignition disabled, and see if the terminal voltage stays up pretty well. I've used starters as high-load battery testers for some time when I don't have a carbon-pile load tester handy.
With a voltmeter attached to the battery posts, disable the ignition system, crank the engine for 15 seconds and watch the voltage. With the starter still running after 15 seconds, a 12 volt battery should stay above about 9.5 volts, or a 6-volt should maintain about 4.5 volts under the same test. There needs to be enough terminal voltage available to power the ignition even after an extended cranking period.
Jerry
