Tie the two white wires together, tape up and place inside the harness - they are a series of feed wires to your dash bar-graph tach.
Disregard the gray wire; it is an extension of the fuel pump feed and isn't necessary for a daily driver. Tape and stow in the harness.
As a footnote, if the tach doesn't work, tying these wires will fix that. However, if the tach goes full tilt, it's defective and needs repair.