Since my engine will be 650HP +/-, most mechanical pumps won't do. So I thought I'd use an electric. Brent just told me about the RobbMC 1100 HP mechanical pump.
RobbMc Performance Products - Ford FE 1100HP Fuel Pump. It's almost as pricey as an electric and requires a regulator, but I guess the plumbing is slightly simpler. Again, I'm torn.