adding underdash powerblock...switched and un-switched

There is only one source each of switched and unswitched power so that is where you will have to "get" it.

Switched "ignition run" which is hot ONLY in run feeds the cluster and a couple of things.......warning lights etc, and then out to the engine bay

Switched accessory power comes off the ign switch and feeds down to the buss in the fuse panel which is switched

"Hot" full time power is the OTHER buss in the fuse panel.

You need a service manual. I've posted this a skillion times. Maybe even a squadamillizillion times
Investigate the links below:

Free service manuals

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