Cool swap James!
The wiring is the easy part
Step 1 is finding the bulkhead diagram for your year and engine.
Next unbolt bulkhead connector from the firewall on the engine bay side (actually you remove it from the back of the fuse block under the dash). Pull back the loom and crap from the engine bay side of the bulkhead connector. You will see that it is two halves. One half (right side) goes to the lights. Remove this and set it aside with the grill. Nothing here changes.
Next is the left side. This goes to the battery, engine, pcm, and underhood fuse block. It's easier to remove this and set it up on a table than it is to try and thin it out on the firewall. Start by pushing the pcm connector through the firewall (none of this will get re-used obviously) then unplug it all and lay it out on the table.
Refer to your bulkhead diagram and remove what is unnecessary. Basically you keep all the bus circuits (powering the alternator and under-dash fuse block) gauge sending unit wires (for your dash), alternator wires, coil power, PCM power wires, and the starter solenoid wire. There's some others but it's been a while and I can't remember. If you get me your bulkhead pinout diagram I can tell you exactly what to keep and what to remove.
Also, keep the water temp and oil pressure sending units from your 4 cyl engine so you can put them in the 4.3 and keep your factory gauges.
Once all the factory engine wiring is removed, you can start on the S10 engine harness. That's pretty easy too.