The 390 in my 65 country squire does not fill the engine compartment fully but a super duty might,I keep forgetting to bring a tape measure to that junkyard but I definately want to see if it is similar to a FE. Any way to tell the cubic inch on those motors by looking at them?,hmmmm my 70 F250 has a tired 360 and a 534 would wake that truck up if thats what it is.