Well,everbody has a differnet idea of drivable.i run a 710 cube 1050 hp motor in my pro street car,and it's not bad to drive with a 4l80e it does ok on mpg,did 16 mpg on a road trip.
It's pretty cool when a guy in a import pulls up and you can nail the throttle at 80 mph and do a burnout
But mainly these 1000 hp rides are bragging rights.