i wouldn't worry about it with the built motor. Just get a fuel system and run the car on e85 and test your fuel at fill ups to verify you are getting good fuel. It will be pretty difficult to tear the motor up un less its just plain abuse.
If it makes a difference: in my OP I said I used 91octane (pump gas), but I Mis-typed that.... I am using 93 octane (pump gas)....