FWIW, on my 511 CID, using runs in comparable weather condition, the E85 was quicker by about a tenth. The torque improvement may be more than the hp improvement, but I just use the timeslip.

110 Gas: 83F, 47%RH, 29,84"Hg, 9.51 at 139 mph
Pump E85: 85, 50%RH, 29.79"Hg, 9.39 at 140 mph (worse conditions than gas)

110 Gas: 83F, 23%RH, 30.11"Hg, 9.43 at 139 mph
Pump E85: 83, 39%RH, 30.06"Hg, 9.34 at 141 mph (worse conditions than gas)

And in cooler weather, the difference will be smaller.