I've always thought the Ford Ranger Spring would be a good swap. Of course, you'd have to use the Ranger Shackles/hangers. They're 2.5" vs. 2" so, they should add some stability to the truck.

http://www.sdtrucksprings.com/index.php?main_page=product_info&products_id=1508

http://www.sdtrucksprings.com/index.php?main_page=product_info&products_id=9417

http://www.sdtrucksprings.com/index.php?main_page=product_info&products_id=9660

There's this kit too

http://www.classicperform.com/Store/1947_59_Trucks/4754RLK.htm

1954 3600 Chevy Truck
"The Fake Truck"
In the Stovebolt Gallery
More pix on Photobucket