Technically, you are correct. The LS1 T56 bellhousing will bolt to a SBC using 5 bolts, but GM intended the use of 6 bolts for a reason. Check the link below for the adpater plate.Mike is wrong about the LS1 bolt pattern. It is identical to a SBC, save one bolt. The second bolt from the top on the right hand side is not tapped in a LS1. You would use five bolts between the trans and engine rather than six. No adapters are required.