[dave2953]

You can swap the arms from a 73-87 truck and 88-91 'burbs. They will work with the existing crossmember. I would imagine you'll want to upgrade to disc brakes as well, correct? If so, you can swap the entire crossmember from one of the aforementioned trucks/'burbs or you can swap the arms and move everything else over. When I swapped to 5 lug, which was just done recently, I changed out the entire rear axle. I obtained one from a '79 half ton truck.