adding 4'' lift. what needs to be changed

[gmc 2500 4x4]

lookin to put in a 4'' lift kit in my '69 gmc 4x4 3/4ton, dana 44 front, and dana 60 rear, front has closed knuckle. is this just a drop in deal or is there more involved? at moment rear has 7 or 8 leafs plus helper springs which will come out, front has 3 leafs. will there be any driveshaft issues? and who sells a good setup? thanx, paul