i have 2 3'' blocks on each side stacked up

 

I have measured in the past, 5.5" I think it was.

 

the sky jacker suspension is to exspensive for the quality of the material but you can get ahold of madison spring in madison wi and theyll hook you up thats what i did or northern spring there also good to go for what you pay for a name brand you can get custom made springs thatll out last the truck