Re the 400 for my 55. I found a chart listing dimensions for various Ford V8 engines. Vs the 289/302 the 400 is wider x 2", taller x 1.5", and heavier by 100+ lbs.
Having seen that the shorty headers on a SBF are a tight fit in a 55 an additional 2" won't make headers any easier in my 55. My...