I'm trying to install some Belltech 3" drop leaf springs ( http://www.summitracing.com/parts/BEL-5952/ ) on my 03 Sierra and the U bolts I'm using aren't long enough. When I install them there is hardly any thread sticking out. These U bolts were originally used with my Hotchkis 4" drop springs which after measuring were clearly not as thick as the Belltechs. It looks like the current U bolts I have are 7 inches long (measured from the inside), and I'm thinking I need new U bolts that are at least 7 3/4 - 8 inches long.

So does anyone have any tips on how to be sure to get a properly sized U bolt? I was thinking of getting factory U bolts but I'm not sure if the current U bolts are factory or Hotchkis supplied U bolts. Really wish these Belltechs came with new U bolts, or at least instructions mentioning which U bolts to use....
Any help would be most appreciated.