Thanks guys!
Had some weird storm clouds outside just like cloud city...
Yes, easy swap. Two things to keep in mind were:
1) King recommends that you heat the gloves before forcing them onto the forearms -- the pegs inside the gloves will fit the Kaustic forearms but it takes force. Put the gloves on BEFORE you put the armor on Vader.
2) the ball joint for the head is larger on the Kaustic than the one on the Sideshow body. No worries -- the Kaustic peg fits fine with no extra force which was surprising.
Its a very easy swap. Trickest part is futzing that damn cape and robe -- I hate them, I hate them, I hate them...