It's a low-revving truck engine because that's what it was designed to be. Listen to the engineers who designed it--they intentionally traded off high revving because it wasn't useful for the targeted usage. They needed an engine that would run under a near-constant load in a relatively constrained RPM range, so that's what they designed the engine to do
IMHO, trying to make it a hot rod engine for a Mustang is like trying to make a half-ton truck engine out of the old Ford 3-cylinder tractor diesel. Yeah, you might be able to do it, but that doesn't mean that it makes any sense; as was pointed out above, there are much better starting points if you want Ford big block performance.
FWIW, I'm sure someone will do it as a one-off just because they can (I wouldn't be shocked to see someone like Chip Foose do something like that for a SEMA car just for the hell of it), and that's certainly cool, but Ford won't put it in anything that didn't get the V-10, which means there won't be enough volume to draw aftermarket support, which means it'll be relegated to the land of one-offs.