happy new years folks..
Anyway,the flex disc is to allow for the unibody to flex and to allow the engine and trans to exit under the car in the event of a headon smash,not for misalignment of the trans Same reason the engine mounts collapse every 10 years,they are designed to rip away.
Because I own a 6.3 which eats flex discs I can say from experience that they must be well within specs if you want any life from them.
Does the use of the spacers place the crank center l inline with the center bearing ?
On the M100 conversion it dropped it 50mm below the centerline which forced the issue and we installed two uni-joints. Very big ones as it happens . The car has been driven to 280KPH on the autobahn without a problem.