If you do a general search of the web, I don't doubt you will come up with lots of plans, but I don't personally see the value of it? You can go to Lowe's or Home Depot and buy steel workbench legs with instructions for attaching them to a top. I didn't even do that. I made both my benches by building a 2x4 frame put together with deck screws, so I can disassemble them. I did use plywood for the top, to get a stronger anchor for the press mounting screws. I also made it 40" tall, rather than the usual 36", liking the height a little better for operating press handles while standing. One fellow I know has a small shelf added just for powder measures so they are up high enough above the bench to get his loading trays underneath.
Beyond that, you just have the addition of a drawer or two for larger tools. Personally, I just use plastic bins and drawer sets for dies and other small stuff. I put a shelf under my bench that holds a lot of my bullet stock. I used cheap plywood for the top, then used flathead screws to put a tempered masonite top surface on it. That makes a surface you can replace if you beat it up or spill liquids on it. Had I to do it over again today, I would have used whiteboard so I could write temporary notes on it.