I'm your height and age but about 195 lbs. My DL 3RM is 325, with hook grip. I can DOH 305 for 3 reps -- my back is barely stronger than my grip.
I personally prefer hook over alternating because I have trouble controlling the "windmilling" towards the supine hand in alternating. Also, hook is well-suited for my long fingers -- I can actually start a little higher this way. But it hurts.