The energy density of gasoline is higher than with ethanol, so the more ethanol you add the more you "dilute" the energy contained in a particular volume.
Though the knock resistance is higher because of the lower energy. So if you have a high compression engine that "requires" 91 or higher, and you have a choice of 87 "pure" or ~95 E85, you may see better mileage and performance from the "lower energy" E85.
Going with a six-pack traditional carb setup too because MPFI additional expense on a small block is just not justified.
Unless you are bumping the compression and using parts in your restoration good to 8k+ RPM, in which case FI is required for accuracy and volume (especially accuracy at high volume).
No, I am staying in factory range on this 318, around 6,500 redline. Caming it to deliver the horsepower and tq. at the low end, since I will be using it mostly at 1,500 and below. Plus, radical cams mess with the vacuum too much for the outboard carbs to open and close when they are supposed to, according to the big guy at Hensley and others.