Re: What size line should I buy?
Buy the line that suits the rod best. That's most likely a 4wt, but possibly could be a 5wt. The good news is that with that reel, you've likely got plenty of room for line and backing, and that's always better than it being too small.
A local fly shop should have both a 4wt and 5wt line you could try on the rod before you pick which one to buy. Also keep in mind that there are some lines out there that are more like a 4.5wt- SA's GPX, Rio's Grand, and some others.