[johnsjmc]

I assume the pilot bearing must match the flywheel used since it mounts into the flywheel.
Next I would expect any pressure plate will work if it crosses any of the years you are considering. I am putting together a Sachs plate original spec for the 996TT with a disc used in the GT2 and the 964RS LW flywheel.( All new but purchased at bargain prices on Ebay) on a NA 993. The spring on the turbo clutch is stiffer (my research says about about 20%) but not nearly as much as the 999 Sachs motorsport PP. There is alot more info at Rennlist than here re 964/993
I think your best bet is the stock 89 G50 flywheel with ring gear because you then use standard 89 starter . Then you can probably use any pressure plate that fits turbo or NA. The disc I believe should be spring centered 89 style also.. The throwout bearing and sleeve will then also remain standard 89 as the stack should be standard 89 height. I see there are 2 89 flywheels turbo and NA and I assume but don't know for sure its because the turbo and NA used different injection in that year or it could be 2 different thicknesses . I believe they are all 240 mm dia .