The anvil is a 10.63 diameter by 32" high solid steel round. It weighs 660 pounds. I found it a the local recycler.
I had a machinist with a very large lathe to face off each end. A flat platform was built to strap to the side of the anvil so a mangetic drill could drill and tap the 1/2"x13 holes for the bottom angles and the 3/8x24 holes for the post brace and bottom die. It was interestng to try and accurately locate all of these holes.