I would recommend the 39.5" Remote Leo for you. The length will be good for your height, but the board is super floaty which will feel good for your weight. Also, it will last a long time because the skates are so durable.
The Water Monsters or Southern 39.5" would be good also if you need it cheaper.
For your height I wouldnt go longer than 39.5". Remote makes a 38.5" which would be a great length for you (I'm also 5'8" and ride it), but you might like the beefier board.