Hi knowledgeable ones

I am changing over an old touring bike (currently with a 6-speed casette) to a Nexus 7-speed internal gear hub. My question is: what size chainring and rear sprocket should I use?

At the moment I have 27" wheels, with a 28-38-48 on the front (with the 28 and 38 being Sugino Cycloid) and whatever on the back. I also tend to be more of a pusher than a spinner, but have one hill nearby that requires a low gear.