Of course, not all 427s are equal. Quite a few years back I spun a rod bearing on my 1968 SS 396 and was left looking for a donor motor to get me going until I could rebuild the original motor 'right'. I bought a 427 'truck' motor from a guy that had it in his pick-up, freshly rebuilt. I jumped at it, spend a weekend swapping it into the 'Camino (had to drill and tap a boss for the clutch cross shaft and put in a pilot bearing), but everything went smoothly. Until I got out on the road. It ran smooth enough, and had tons of torque, but it would not spin faster than 4500 rpm. After some belated research, I found out my motor came from 1980s five ton dump truck. Designed for low end grunt the manifold runners and head ports are tiny. Of course fifteen years later, that motor is still running strong and the original is still under a tarp in the corner of my garage.