My REPUis currently NA and has the stock 30 pound flywheel with its 225mm disc and pressure plate and it has plenty of grip. By itself, the current setup feels a little on the heavy side. When towing it feels fine. When it gets an SC, the additional rotating weight of the roots blower 'peanuts' add a noticeable amount of extra weight to the rotating assembly. You can feel it when you drive.
Think of it like this: as a general rule, you always want to chose a flywheel one step lighter than you ordinarily would. In other words if you absolutely love the feel of a Racing Beat light steel flywheel in NA form, and countless rotorheads do, you will definetly want to switch to an aluminum flywheel when getting an SC. The extra spinning weight of the SC makes the aluminum flywheel feel a lot like a 13 pound light steel.
Same is true for let's say a GSL-SE flywheel, which weighs about 27 pounds. This flywheel was an upgrade from the stock 215mm 30 pound flywheel in my bro's RX-4 wagon. The old 30 pounder felt heavy. The GSL-SE was a major improvement but we could tell that a light steel would have been too light due to the tall diff gearing of 3.636 and weight of the wagon. We should have gone ahead with it though because he got an SC and once it was on there it felt just like the old heavy clunker 30 pound flywheel and made the car actually less fun to drive than it was in NA form. Strange to tell.
The SC is coming off the wagon and going on the REPU. This is why I need to upgrade the flywheel and chose a good disc and pressure plate combo that will handle the torque and the weight of the truck as well as slippage during towing while starting from a stop etc.