We’re the valves clean on number 4? Intake gasket look ok? Worked on a lot of FE’s early 75 to 80ish at a Ford dealer truck shop. Neat trick back then was to take crank out of a 391 HD (forged) cut snout down to 390 specs. Customer brought his own used motor in to install in his plumbing truck F 250. Turned out to be a 428 super cobra jet engine. Took every tech around the block. Would throw the cleats off the 16.5 split rim mud grip tires.
How much is block bored? Can’t remember the bore over limit. .060 I think because of core shift during metal pore. If someone was going all out on a FE they would have a sonic test checking for core shift. Probably not a issue since y’all have used for 16 years. Just FYI.