At only 265 lbs or so, chalk shouldn't be too much of an issue yet.
Certainly, if you haven't, you'll want to be using a mixed grip.
Also, like Phill said, if you get into the rack, do some fairly high (short range of motion) rack pulls, you should be able to lock out a fair amount, but you'll really have to man up and hang on to the damned bar.
I'm not using that language to be insulting, at all, but the odds are you can generate more force and grip than you think.
Also, with the weight you'll be using, be sure about your form.
Finally, a long time ago when I was having grip troubles, I was sent out to do hammer curls... perhaps after deadlifting or doing chins.