What is the whole point in putting a D2 front driveshaft on a lifted D1?

 

The double cardon joint is the difference.

 

D1's come with a traditional 2 joint - D2's come with failure prone non greaseable double cardan drive shaft. Tom Woods is the way to go...

Here is information about the different types of shaft and why you would want one vs the other
Tom Wood's Custom Drive Shafts - Shaft Selection: CV or non-CV?

Enjoy!

 

On a lifted D1 without castor correcting swivels and/or castor correcting radius arms lifting it will tip the diff pinion up towards the front output housing.

Single cardan u-joint propshafts should have the pinion axis and output shaft axis parallel to prevent vibration. If the pinion is pointing at the output then there should be a DC joint on the output end to prevent vibration.