The obvious tell on an engine that requires a specific balance on the flywheel is either a dowel pin (like some european cars) or an assymetrical bolt pattern
Generally on american V8 engines the manufacturer will offset ONE of the bolt holes
so one bolt doesn't line up unless the flywheel is corectly "Clocked" to the engine.
Ford used a symetrical bolt pattern on the 2.8/2.9/4.0OHV because
they are internally balanced and thus the flywheel is neutrally balanced.
You can mix and match, infact swapping a 4.0 flywheel ont a 2.9 is a popular upgrade.
AD