I did what Tom said. (Always a good idea!) Went to 190 internal, and a fab result.
But then...........I pulled out an old edition of Joy of Cooking (1978). There's a pastrami recipe there.
Two very interesting items:
1: If you are corning beef with pastrami in mind as the end result, you can alter the brine for that purpose. Add a lot of wine, corriander, ginger, paprika and pepper to the brine for the corned beef.
2: Cook that corned beef over relatively high heat---320*! 6-7 hours. Not low-and-slow. Put the heat to that bad boy.