Speedometer Cable Question for 77 Chevy P/U

[77 ChevySport]

Have 77 Chevy P/U with the optional gauge package. Have a speedometer
that is now not working. (But did work) We recently replaced the cable and
it worked perfect. I am going through the connections (two piece) and checking the tightness of the connections.(Cable/Transmission/Speedo Gauge) Cable and transmission connections seem OK. I tried to stick my
hand behind the cluster to check the connection to the gauge and could
not find a way to get to the gauge. Maybe I just going in at the wrong angle.
Can one get to the gauge this way or does the cluster have to come out a bit to get to the gauge. Please advise and thanks if you know. Larry