#3 bismuth. near equal pellet energy to steel #1, 30 more pellets in the pattern. 1 1/4 oz would be fine, but I'd probably go up to 1 3/8 oz just because I like pattern density. 1350 fps or faster will provide sufficient penetration out to 40 yards.
If not bismuth, I'd probably just treat them like honkers and shoot steel 2's, 1's or BB, whichever patterns the best for your gun/choke. Federal, Hevisteel, Remington Nitro steel, etc. etc.
12 g/cc tungsten from Hevishot is just too damn expensive any more for what you get; Hevi-XII is $2.50/shot and the 3" loads are only 1 1/8 oz now. I'd kill to go back to the days of hevishot #4's in a 1 3/8 oz 1350 fps load for under $1.50/round.
If money is no object, TSS 1 oz #7's. For when you want a 185 pellet swarm of killer bees that will blow through the skull of a bird out past 60 yards.