FWIW, I'm not an American, so I'm not entirely aware what old Republicanism meant. I do know old Democrats were pro-slavery and pro-Lenin.
But I am an Adam Smith laisse faire conservative. IMO, what made America great is not protectionism, but free trade and its ability to feed and mechanize the world. How are current Republicans any different than Democrats when it comes to the all embracing of John Maynard Keynes communistic ideals, I'm not too sure? Central Banking, currency manipulation, mercantalism, the dependence on government to solve our economic ills, the misinformed desire to eliminate business cycles (may as well eliminate human emotions while we're at it, funnelling of dollars to big business who should have been allowed to fail (airlines). The list can go on.
Not much difference anymore. Both parties are sliding into socialism, our Constitution is being bastardized, and the ideals of our founding fathers have been all but forgotten.