Transfer Case suggestions
1) Does it have lights or gauges
2) Does it have the clock, if so the e-brake light could be in either the speedo or fuel gauge, if not its in the 4th gauge hole
3) Does it have a tach, then the fuel gauge is in the hole where the clock is, unless the cluster is a 2 ton truck then its a fuel-tach combo gauge.
4) If it has gauges is the oil pressure gauge electric or mechanical
5) The gauge faces are different between the 73-80 to 81 up
6) There could be more but this is what I could think of off the top of my head.
It is possible to install any cluster from 73-87 truck,73-91 blazer but it will take some work because the wiring is different between them.
I meant to change the whole cluster. It's not worth the effort to try and put the electronic speedo into 77 cluster. If you get the plug for the 88-91 cluster and install it and the cluster into your 77 then all you have to do is splice and match. The additional wire for the vss input to the speedo will then run to the pcm. That's how I setup my suburban when we built it. The dash bezel and all existing 77' hardware will fit. Looking at the two you will never know they are different once installled.
