It will be worth the effort, The 73's still have the tucked bumper... ( IMHO the best kind )
You may have to drill the frame rails to support the new brackets...wait, do the 74 rears mount with shocks or steel mounts? ( can't remember ) If they use the steel "strap" mounts, I think the holes in the frame will be ok, if they use the "shock" mounts you will definitely need to drill some new ones.
