The input shaft on the T-50 gearbox only has one bearing on the shaft...

The pilot bearing is there to locate the end of the input shaft and prevent the 
shaft from "flopping around" when the clutch is disengaged. The bearing is only 
working when the clutch is disengaged. At all other times the input shaft and 
crankshaft rotate at the same speed. 
FWD versions don't use a pilot bearing, and it is not unusual for the bearing to 
be missed out on RWD conversions. However, while not have the bearing can  
cause some clutch vibration and noise, I have no knowledge of it destroying 
gearboxes. Just tap the bearing in until it bottoms out, re-assemble, and you 
should be fine. Make sure the bearing is a sliding fit on the shaft beforehand  
 
 Cheers... jondee86