Buy it. I'm 5'8" and have no concerns about fitment (rode over 1400 miles this weekend). You'll like the big motor cuz you'll have the power when you need it and within a month you'll be back on the forum asking how to get more poop out of your bike. I have 4 different bikes and, to me, the Road King is the best all round bike you can get. Great for cruising around the block or around the state. Hope this helps.
ps.everybody will be drueling (or is it drewling) over your Screamin Eagle.
If it's got the 20" windshield, just cut it down to fit. buy one that's too short and you'll hate it. too tall and it'll drive you crazy looking thru it.
You will find when you ride it that the King has a very low center of gravity and it practically balances itself. Once you ride it, you will love it. Like others have said, bring your checkbook. Bring your camera too so you can post the "my new bike" pics. One other thing...Have fun!