I've only recently gotten my first lightweight flywheel car on the road-a 351 Cleveland powered '69 Cougar. Stock cast iron flywheel was 28.6 lbs and AL is 13.8 but I still have a cast iron crankshafts, 8 steel rods, 8 pistons, and a big OEM cast iron harmonic balancer. It didn't make a huge difference in my yet limited experience with it. I see no degradation of driveability or difficulty driving it. I also haven't seen a huge change in how the motor responds to throttle inputs. I say go for it.
