You will need to check the axle code which is on the VIN plate.
AE71 vans had S series diffs which were same as local Sprinters (AE86)
AE71 wagons however may have same as local AE71 sedan, you will know once you check the plate.
You can get tramp rods which stop the tramp, called Caltracs but they are not cheap.
How much power we talking??? I have a 4AGE in my AE71 van and it doesn't tramp