Reference Sheet C75-BRS-1 Four Point Haness - BRS. Installation began with the drilling out of rivets on the Lateral 'L' under top skin to allow alignment of the Cockpit Harness Mount Channel (SD75F30-1). 'L' with be shortened and reinstalled at a later time. I marked up the installation and clamped the parts in place. I noted that SD75F30-4 was sent in the kit instead of 75BRS1-3 Rear Gussets. The difference in the part changes the mount location against the Baggage Back and fails to align with the vertical rivet line under and slightly inside the position of Cockpit Harness Mount Channel. I will contact Zenith (Roger) about this change and options. I noted the plans illustration correctly showed the part 75BRS1-3. A second question developed regarding placement of SD75F30-1, Cockpit... Mount Channel. I noted this earlier when plans reviewed. The Mount Channel rivet number does not reflect the number called for on the plans. Alignment however is not an issue.