Mike, you spent a ton of $$$$ on your engine, and you are going to trust any in-tank stock fuel pump, or even 2 of them to perform and be reliable at 800 HP?
Do it right the first time, and install a 1000 HP system and never look back as you will have a good safety margin, and it will be very reliable.
How many times have you seen one of the double pumps fail at the wrong time with disastrous results? Not many, because people do not post their mistakes, but I have seen it happen many times.
Make sure it is done RIGHT the first time, which will cost very little more, and even less, if the first system does not perform to your expectations.