OK, that is piece of mind I guess.
I fired out a barrage of emails and PMs over the weekend and Core-Tac had the easiest solution for my issues. I can see by the tracking number that it is already on its way to me.
In short, I bought from them because they had the product on their website where I could decide it was the right one for me. I could tell what size the break was and that it had the right threads. I could also see that I liked the design of the brake.
I just wish they came up on google when you search for muzzle brakes!