Removing paint spatter from Postwar diesel truck sides

I would try a Dremel tool with a wire brush attachment.  I have had good luck with it removing rust and it rarely leaves scratches.  I usually use mineral spirits to clean off the grime. If you soak it long enough, it probably will make it easier to remove the paint using the dremel.    

The Simple Green just isn't strong enough.  I have great results using "Castrol Super Clean", purple jug (1 gal.), that I use for stripping die cast and plastic parts.  Use it full strength, with an old toothbrush, and rinse it off when you are satisfied with the results.  I would shy away from using the Dremel with wire brush, as it tends to leave scratches, especially if the part is plastic.  The only time I use the wire brush and Dremel, is if the parts are die cast or metal, and would most likely be repainted, or even "blackened-Gun Blue".

Plain paint remover should get the silver paint without hurting the original black finish, which wasn't paint.

Needless to say, put a little bit on the back to see how the old finish reacts. It may be affected somehow - paint or not.