Can a 74 Chevy 350 4x4 use 1 to 2 gallons of E85 on a full tank with out damaging it?

I would avoid using E85 in any pre 80's vehicle with any rubber in the fuel system. Ethanol will dissolve and swell rubber that is not intended for use in alcohol. It will also pick up a lot of debris in the tank and likely that age of vehicle there is a lot of debris in the tank.

1-2 gallons should NOT be an issue, but I would NOT run it in my car until I have 100% inspected the entire fuel system, inside the tank and out, and ensure all rubber has been replaced with modern rubbers.

One time, probably ok, but definitely not consistently.