You shouldn't be checking for "power" at your senders. Especially since these would be 5V (rather than 12V) sensors.

Let's start with something basic- can you verify that the Tachometer is plugged into the TACHOMETER harness, and that the Speedo is plugged into the SPEEDO harness?

Also- please check that the harnesses have GAUGE END and Junction Box End in the correct orientation. It DOES make a difference.