How does the Rallye Dash Tach hookup?

This is the pic I should of used in the beginning. Looking left to right, the 1st, 3rd & 5th blades are open. If you were to look at the front side of the block, the far right fuse slot (under the 5th blade) is the open one labeled INST LPS.
This was a brand new wiring harness from Y1 (made by M&H). In the '71 Chassis Service Manual, Page 8-67 shows this fuse block with a fuse in that slot ?
So, which one of the three open blades can I hook the tach to?
Thank you all for your comments.