If it were my money, I don't think I'd go with a solid billet to start with. Too heavy(and ya pay by the pound!) and why turn most of it into chips if you don't have to? I'd make a weldment...probably 1/4 or 3/16" plate. Cut it out, add some ribs for stability, then finish machine the critical surfaces. A little more labor but a good weld shop could make it happen pretty in short order, I would think.