Can you get a pneumatic impact wrench on it? If not, you can apply heat from a propane or acetylene torch and use a wrench or breaker bar with a pipe on the end. There is nothing to hurt there since you don't need to get anything really hot to free it up.
Carl


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission