Oh yes, are you ever in for a smile when she comes back to life!! Very similar to you, my 1969/70 Commando S did not run for 30 years (except it was not frozen), and I could never ever sell it. After a few parts and polish, when I kicked it over again to start it last October, I was in my 20s again. Smile every time I look at in my garage. Waiting for Spring -- if it ever comes!
Its a little late to comment on the black cylinder paint, but there are three factors in heat transfer -- thermal conduction resistance, convection, and radiation. As long as it is not too thick, the black paint (especially flat black) will radiate heat more effectively than aluminum color, and this offsets some of the insulation effect of the paint. The conduction heat transfer that you loose by the paint insulation effect is, like any insulation, worse as the thickness increases, so thinner is better (i.e. thin coat from a rattlecan). I have not run numbers on paint films, but I would guess that the heat transfer resistance of the convective coefficient to air is much greater than the thermal conduction resistance of the paint (with any reasonable thickness). So I suspect you have to have a pretty thick paint film before there's an issue. For that matter, think of dirt bikes that are caked with dirt and still running OK. You'll be fine.
(If anybody is actually interested, I could run some numbers to compare typical paint film thickness with loss of heat transfer. Usually, that's the sort of thing I do for work.)
