Any 1 ton rear end is going to big, and I would not suggest going with smaller brakes. Try finding a 3rd member from a '67-'72 3/4 ton, they are intrchangeble with your current rear and I have seen them with 3.55 gears. This would be easier than swapping rears. If you do want to change the entire unit then get a 14 bolt full floating rear from a '73-'87 c/k 30. If you want to do a 4x4 swap get the Dana 60 from a k 30 as well.
