As alluded to by others, there has been an update to the RV-7/8 fuel tank design that allows for providing predrilled z-brackets for the fuel tanks.
At the time of the change-over in part production, the updates to the plans were not yet completed but since the change in actual build process is rather minor (the updated parts basically just pre-complete some steps for the builder) the decision was made to start supplying them in the kits ahead of releasing the updated plans.
Builders that have the new parts should just skip the steps in the manual related to marking and drilling the z-brackets for the bolts. Then install the nutplates, mount the z-brackets to the spar web with the specified bolts, and cleco the baffle and ribs in place.
From that point on the build sequence should be the same as described in the manual.
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Van's Aircraft Engineering Prototype Shop Manager
RV-6A (aka "Junkyard Special ")