I'd use either .45A with some modifications for weapons and inventions, or perhaps the Geezers 'Shut it!' 1970-rules from Killer B. Or combine them 
Good call, or maybe "Chain Wars 2" from Two Hour Wargames, which covers pretty well every 20thC scenario.
.45 Adventure is very good, of course and also very good value, but CR2 is free and you wouldn't need to make too many changes.
Haven't seen "Shut It" so can't comment on that one.
Oh, what the heck, buy .45A and download CR2, then you have the best of both worlds
