Not sure if the year of manufacture is relevant. If you're looking for an upgrade on your truck, the wagon springs aren't going to cut it. Adding a helper leaf spring might be the ticket. The fastback I owned had a 2 leaf spring in the rear end (it was like riding on a rubber band) and it actually snapped the right side spring - my bet from the PO doing burn outs and beating on this poor thing. The wagon springs were 4 leaf and were considerably stiffer than the springs in my Lancer fastback. I took the axle shackles and the bottom plates as well. If my memory serves me well the only mod I had to perform was grind off 2 small locater discs that were tack welded onto the axles. I used that wagon to haul a whole lounge suite and regularly loaded it to the eyeballs and it never bottomed out or scraped. Unfortunately I don't recall the model of bushes I used but they were Nolathane branded. I guarantee it will never bottom out in a lightweight coupe unless you take it for some serious flying lessons.

p.s. you could also swap the front sway bar from the wagon. They are hell thicker but you'll need to get the 'D' bushes and brackets to go with it. If you can find a wrecked wagon, compare it with your car.