For the 2JZ-GE are the front and rear driveshaft flex discs interchangeable and what is the specific oem part#?

 

They are called drive shaft couplers or couplings. They are the same front and rear. I think it is 37511-24010

 

37511-24010 about $246 each online, still available from lexus in 2-3 days

 

The driveshaft is balanced and matched to the trans tailshaft and the differential. So if you ever remove it you need to make sure to mark the location of everything so you can reassemble it the correct way or else it will vibrate pretty badly.