Brie,
I echo Parkwood's thanks for your dedicated service. Your F100 has tons of room up front, enough to sit on the inner fender with your feet on the frame to work on things under the hood. I saw a F100 of that era (maybe a '60?) with a 4.6L Mod Motor, and it still had room to spare. The Mod Motor is super wide, so I don't think you'll have any problems, other than either finding the right mix of motor mounts or fabricating new mounts on the frame. There may be someone here who can guide you to an OEM mount that works.

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