The 8 spyder's can come diff's only or with ultralight housing's, making them more expensive, but you don't need the housing's for the hybrid bulk's.
With housing;
http://www.unlimitedengineering.com/...re/13540B.html
Without housing;
http://www.unlimitedengineering.com/...ore/13543.html
You need 2 of the last link for 1 truck.