These guys did not overheat, they flat ran out of HP at WOT for minutes at a time.
I know the feeling. I towed, and still tow with a 200 HP (now around 225 HP) turbo diesel. I have also towed the same grade with 200 HP truck a few times. I was down to less than 30 MPH though.
As far as the fuel thing goes:
Nitromethane has around 5000 BTU's/LB
Methanol has around 9,500 BTU's/LB
Gasoline has around 18,500 BTU's/LB
Engine size for engine size, boost for boost you can make more power as the BTU's go down for the fuels above.