Installation pics! Hope somebody will find it useful.
Backside of the Blazer/Jimmy 4-window switch.
Bulky and expensive 10-way connector from GM. I decided not to splice wires into the original harness, so I ended up cutting this connector and only using a part of it.
Cheaper route would be to add a salvage yard, 2-switch connector and make a second harness.
Used a wire hanger to fish the new wires through the kick panel grommet (%^@#*@ PITA).
Shot of the kick panel grommet from the inner fender. Great place to slice/scrape your hand.
Shot of the new wires wrapped in harness tape and the modified 4-switch connector.
Finished. Might use the 4th switch for my power antenna, possibly my exhaust cutout, or maybe two ghost/security circuits.