Find a good dealer and have them fit you. Bike sizing isn't nearly as exact as, say, shoe sizing (and you'd never buy shoes without trying them on). Most people think effective top tube length (TT) is the most important measurement when sizing a bike. It's key to determining how you're going to sit on the bike, so I'd suggest you get that measurement on your current bike (assuming you like the way it fits) and find the SJ frame that has a TT measurement closest to that number. Start there and work with the dealer to fit the bike by adjusting saddle height, position (fore, aft and angle), stem height and length (they should be willing to swap for a different length stem when you buy the bike).