i would not ever just try to testdrive it and hear if it grinds, thats a total suckfull way to go about it.
when you install the juice just get the car up on jackstands and see for yourselfe that nothing grinds and that everything gets the clearance it needs.
you dont testdrive to find out that kinda stuff cuz when you hear it ginds you allready fucked the u-joints.
if you see that yourdriveshaft is pushed too much into the tranny when locking up you'll have to shorten it or get a slipshaft.
i would get a slipshaft.