As I said, driveshafts are the least of your worries. From your original question it sounds like you may expect this to be a bolt in swap - and it is far from a bolt in swap. New brackets (lot's of cutting and welding), new brake master (likely), clearance issues in the front due to diff location, and either not too bad or a nightmare getting the old stuff off depending on the year of the axles, brake lines, parking brake cables, etc. We don't know anything about you or your abilities, so don't take offense to this - but it sounds like you need to do quite a bit more research.