Because the 68RFE transmission does not have the passenger side test port like it's predecessor, you will need to find another location for the transmission temp. gauge sender.  Here we have installed it right in the cooler line with a manifold T (Part #: FTG-MFD50). The sender is bathed in the hot line of the transmission, giving the driver instant readings of the ATF.  Another solution is to use the DieselManor Transcender™ (Part #: DM-TRS50). The Transcender™ simply attaches to the outside of the same cooler line, but instead of cutting into it like in the above picture, the Transcender™ simply clamps to the outside of the line.