Hey Gary,
That's the correct flywheel for a 3.2 Motronic paired with a 915. You're correct the trigger wheel is the flywheel "teeth" that look like they're for the starter gear to mesh with. They're actually flattened teeth that the DME reference sensor detects for ignition timing. The actual starter gear teeth are on the separate ring gear that mounts on top of the clutch housing, just like your SC.
If you want to take advantage of the opportunity for light weight clutch assembly, i'd instead consider the Kennedy Eng. Products clutch. It's much lighter than the Sachs aluminum unit. They make two types- aluminum housing with iron internal pressure plate or aluminum housing with aluminum pressure plate & a carbide friction coating. The all aluminum one is a really nice piece. Used to have one on my 3.2L racecar
Porsche Pressure Plates
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/680787-225mm-kennedy-eng-stage-1-clutch-915-trans.html
Kennedy also makes puck style discs but they're actually just rebranded Clutchnet discs
VW & Porsche Discs
Clutch Discs Clutch Kits | Clutch Discs | Pressure Plates | Flywheels by Clutchnet (626) 448-7432
20% off and free shipping is the usual winter sale from Clutchnet