You probably blew your fusible links. All power for the cab in stock wiring comes from the battery voltage lug of the starter. You should have a big 4 or 6 AWG wire running directly from the battery to the starter. Connected in the same place on the starter will be 2 smaller red wires (10 AWG?) that lead to the bulkhead connector under the wiper motor.
An easy test to check if your fusible links are blown is check for continuity with a multi-meter between the positive post of the battery and the backside of the bulkhead connector. Here is a snip of that part of the wiring diagram with some marks for each end of one of the power wires from the start to the bulkhead connector
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Something to keep in mind if your fusible links are blown, is something most likely caused that to blow. It may be stock 40 year old wiring so it could have just failed, but odds are there is a cause for the blown link. If you go and just replace it, you risk just blowing it again down the road.
