Do you have Scott Landis' "The Workbench Book"? Because, it's in there! I havn't made that bench, making one of my own design. You would have to go to a blacksmith for some hardware, like extra large hold-downs, have them made out of spring steel, not iron.
Maybe as well the adjusting hardware for the lower end of the leg vise, but in the book that "assemblage" is made of wood. The screw for that can be the *tail vise screw* from Lee Valley, it is 1-1/8" thick, and that whole vise is completely removeable so the giant hold-down can be used in the same leg.
As far as wood, you can use any nominally hard wood, like 'hard rock sugar maple', euro steamed beech, birch, white oak, SYP if available (I would avoid white ash and red oak because of the open grain structure, and softness) all would be my acceptable choices.
As massive slabs are very hard to find, I would laminate commonly sized 8/4 -
12/4 stock into a 4" - 5" thick top, cutting in the dog holes first with a hand saw, like a Ryoba and chisel. Simply into the standing sides of the boards.
And, you couldn't stop me from using at least five 1-1/2" thick allthread rods from front to back, outside holes countersunk for the nuts. That means each board would have to be drilled during the process of cutting the dog holes, your choice how you do it.
And for laminating, you would need many 3/4" pipe clamps and wood jaw pads for them, cheap ash or Philippine mahogany. A row for the top and a row for the bottom, every 6 to 8 inches. Do two to four boards at a time, then the whole thing.
Getting the clamps tightened down in an even fashion, not one end to the other, is a big intensive job so I would use a glue with a long open time, such as Garrett Wade's 202GF. And you can use your allthread as part of the clamping for every assembly. A very easy design but hard work, I suggest check out the book.
Do you have any reciprocative reality of your own? Anyone else?