That 455 stock is a pig compared to many on the road todat. Even the 6 cylmustang would shame it.
There's been people with stock 1971 Buick GS 455s that have posted confirmed top end speeds just above 160mph, and some Pontiac GPs will run about the same top speed. The stock 6cyl Mustang won't do that.
Those 455 Buick and Pontiacs ran into the 13s ET in the 1/4 mile on redline skinnies. The stock 6cyl Mustang will just about get into the 13s.
If there's any weak point in most of the 'B/O/P' 455s, it's the valve train valley casting in the block's upper end. I've seen more than one crack and suck an intake valve down into the cylinder. One of them right in front of me.
I'm thoroughly a fan of computer controlled fuel-injection and intercooled turbocharging, but GM is still making enormous displacement crate engines available like the Chevy 572s that will run well over 1000 horsepower (and more importantly, ridiculous torque figures) on regular old 92-octane pump gas. I can't imagine anyone wanting to drive one around town as a daily driver though.