[Mahler9th]

Isn't "street driveability" subjective?

Everyone has their own definitions, right?

And if there are a number of prospective parts in question wouldn't there be multiple variables to consider?

What is the goal of a lightweight flywheel in this thread? That appears to be unstated.

The Mini had the final drive changed. In 1972 Porsche language, that might mean a change in diff or gearing or both. The flywheel has nothing to do with that.

My 911 is a '75, and it has a 3.6 in a config that makes about 330bhp. Car weighs about 1900 pounds. I use a lightweight Fidanza flywheel (requires a slight mod to the case for clearance). I now have an all alu racing Sachs motorports clutch (sometimes called an RSR clutch). These are all alu, very light and nearly unobtanium. The Kennedy stage 2 is similar but a bit heavier. These have a very high clamping force. I use a 6 puck racing clutch from Clutchnet.

This is an "on/off" clutch set up compared to all stock Porsche set-ups. I also used it when my engine was a 3.8 and made about 370 bhp.

I can drive my 911 on the street-- it is a 75 so smog exempt in CA. My clutch set-up is very challenging when I drive on the street.

So the answer is as always... "it depends."

Everything else being equal, would a lightweight flywheel do anything for the OP? Whether aftermarket like the Fidanza, or a lightened stock unit?

The answer is YES. If the alternative flywheel is 2 pounds lighter than the one in there now, the car will weight 2 pounds less. Whether that matters to the owner driver is completely subjective.

These questions have all been asked and answered in these Forums for decades. And for decades before that in publications like Pano.