Those with Sulastic springs/shackles.

[Yondu]

I installed Sulastic shackles a few months ago.  I got what I thought was a good deal on eBay for almost new shackles. Installed, the driver's side is basically maxed out (5 3/4" bolt to bolt) and the passengers side is about 3/4 maxed out (5 1/4" bolt to bolt). 1/2 would be where you want them. This of course lowered the rear of my truck about 1/2" or so.

 

It appears they're too light for my crew cab standard bed 4wd truck. The box says 151-409 on them which I'm told is their weight rating.  

 

I've contacted Sulastic but it sounds like the next step up is the HD version which is probably too firm for my truck.  Anyone who has them able to comment on where there's sit and what the weight rating is? The person who emailed me wasn't too informative.