The '53 Mercury flathead with '40 trans. sits in the frame fine. The issue = the fan will be hitting the radiator big time. I am sure this has been done neatly, but what exactly has been done is my question. Shorten the fan shaft is the first guess. What is the minimum distance between the fan and radiator. Dad says 2" That seems impossible. We prefer to use the '40 radiator but have a '53 F100 rad. as well. Perhaps a past post direction.