I've run several games in this time period, usually using homebrewed add-ons to existing systems. In college, I ran a game in this period using Mage the Ascension rules. We used Privateers and Gentleman as a useful reference doc (which it does quite well, although the RPG rules are, shall we say, dated.) I then ran a couple of con games using Ars Magica as the system, with firearm rules bolted on. That worked quite well.
My recent games in this time period have been using a home-brew rule set I call "Heroic Dread," based off of the Dread RPG (which uses Jenga instead of dice and is awesome). Basically, I add on skill numbers so the players have more of control to let them feel more heroic and I add an extra-lives sytem. It's been terrific fun and has worked really well. I hope to post more about it soon, but I'm crazy busy right now (getting ready to run it at a house con, actually), so that will wait until next week or later.
If you like rules-light approaches, I would advise grabbing your favorite rules light game and then just redoing the theme to make it work.