Nice job M! Here are a couple things you might try next time. Apply the pastrami rub the night before, wrap the meat in plastic wrap and into the frig overnight. Your IT of 160-165 is spot on. After the smoking/cooking session, wrap the pastrami in a piece of tin foil and allow to lay on the counter until able to handle. Unwrap the meat but save the foil as you will need it again. Wrap the pastrami in plastic wrap and then the foil you saved and place in the frig for a day. Two, if you can wait that long. Thinly slice AGAINST the grain
and you have something like this.
This is not my original recipe but some tips I picked up on a different forum. I have made pastrami several times and it works for me. I also use a commercial pastrami rub, Uncle Louie's Pastrami Rub available at Great American Spice Company because I am lazy and it tastes great but you can certainly make your own.