Kevin,
A lightweight flywheel will cause the motor to rev quicker, but that comes at a price if your gear ratios aren't ideal. It will be more difficult to lug the motor at slow speeds and could really mess up your starts from a stop , (especially from a hill slope)
My 72 2.0l had a near stock clutch / flywheel ( weight near 30 lbs) I was only going to use the car for racing so I purchased a twin disc clutch/ aluminum flywheel (Total weight 15 lbs) And boy did it wake up the Throttle response! But the price was a clutch that was all in or out, and much harder to engage easily. The other consequence has to do with the flywheel/ crankshaft balance and harmonics, and what will happen to when the vibrations get to the nuts and bolts. I literally had my alternator unscrew the small bolts that held the two halves together, and that was with a smaller (underdriven ) crank pulley. That never happened before, same motor, same performance mods. It really needs to have the Crank rebalanced with the Flywheel or a harmonic balancer added to the front of the crank. Racing mods can cost you down the road, and seldom offer a great benefit without consequences.
Pintosopher, Stuck on revs..