For the metal to metal up front you might want to check the front drive
shaft against the exhaust pipe. sometimes the clearance in very little at
best and a lot of times it rubs.
My 4" RC lift came with shims on the rear leafs as well as the T-Case drop
brackets. I installed them both and still have some vibes over 62 MPH on
the highway. I would install the drop kit for now and save up the ponies
for a Slip Yoke Eliminator and also replace the double cardan drive shaft.
This is what is needed for the best operation and no vibes in your drive shafts
due to steep angles and wear. You can get the angles correct, after identifying
the proper pinion angles and T-Case angles, and then shimming accordingly.
The better fix is the SYE.