think about what the spacer does. It lowers the coil assembly 6" so that the suspension is in the correct geometry relative to the 6" differential and lower a-arm drop. The procomp spacer is only 4". I don tknow what this would do, but it couldnt be a good thing. Why do you want to do this anyway?oneill94 said:Would it be safe if I used a 4" Pro Comp spacer with the 6" Trailmaster spacer?