I have a 78 cj7 with the 304,t400,quadratrac drivetrain. 4" lift with 2" longer shackles. The driveshafts are stock. As long as pinion and transfer case angles match, you should be fine. If you do a transfer case drop and raise the pinion the same amount you drop the transfer case(in degrees), you should be fine. Definately check the articulation like CJ said. He was writing this post at the same time as me and beat me to the punch. Man he is fast! As far as the frame, any part that is rusted needs to be cut out and replaced by a good welder. Cut out a little past the rust so you have clean strong metal, use some cardboard templates to trace onto the proper gauge steel, and you are in business. Brace and gusset any repairs the best you can. Better safe than sorry in this department.