I am pleased with my effort and the result is good in my humble opinion. The Warehouse drop target is one of the better examples of things lost in the transition from sample machine to production run machine. Game play is faster and improved with the drop target installed.
For those of you that have the production machine, you may know that the current software supports the drop target. You can "mod" your machine with a few hours of effort and a few parts that are readily available.
Instructions below are for reference only, and I will not be liable for any damage or harm to your machine or yourself.
I suggest patience and going slow, so as to avoid any irreversible damages.
You should see 4 factory dimples underneath the playfield around the Inspector badge for the Warehouse. You should also notice a 3-pin molex connector built into the wiring harness that has no match in that immediate area. The dimples are for the drop target assembly itself and the 3-pinner is for the drop target switch. You will need to build up the wiring for the two coils and create a connection from the switch to that 3-pin connector.
The parts I used included a new single self-dropping target assembly (A-15211), the actual drop target itself (I used an AFM red #03-8750-2, but you could use black #03-8750), two pairs of 2-pin molex housings (male and female) that can accomodate 18 guage AWG wire along with two pairs of molex pins male & female (.093). These are for the 2 coils on the drop assembly to make removing the whole assembly easier, and any color of wires will do. I suggest 7' of each color, and you will have some waste at the end of the process. I used white with orange, white with black, blue and pink.
You will also need a 3-pin molex connector (better to get both a male & female), to use for the drop target switch, and the wiring for this short run (two different color strands of 6" or less) uses a 22 guage AWG wire, along with a pair of male/female .062 housings (you may not use both sides). You might also want to have a supply of small zip ties if you prefer to snip the ones on the wiring harness instead of pushing the wires through.
Tools that you will need include a drill and/or dremel, an IDC punch down tool and a molex crimper. I used a few different drill bits, a Dremel #453 sharpening stone (5/32"), a 2-pack of 3/8" x 1" Kobalt grinders (Lowes item #0236542). You will also need a soldering iron.
I had recently shopped the machine, so I started by pulling the parts on top of the playfield that get in the way. It would be better to do this while the playfield is stripped down.
I attached the drop target assembly using the 4 dimples and then held the loose drop target in the area of where it would pass through the playfield. I used a pencil to outline the area and then drilled my first hole from the top with a small drill bit to get a good bearing on where the center of the target, as well as the rest of it, would pass through the playfield when I was done. Basically, make the hole carefully, using the target and assembly frequently to check that you are lined up and sized up correctly. My finished opening is smaller than factory, but it is easier to enlarge it than to try and fill it back in.
For wiring, build up the drop target switch and test it. The green wires go to the middle and the white wire goes to the non-banded side of the diode.
I soldered the drop reset (green) coil to the right ball gate at the top of the playfield (see the white with orange band wire that I added to the same lug as the red with orange wires). For the small drop coil (yellow) I soldered it to the ball launcher coil (see the pink wire that I added to the same lug as the red with brown wire).
For the other sides of the drop assembly coils, I used a white with black wire and a bluish-green wire. I pulled the wires all the way up the wire harness (new zipties would have been preferable and faster). When I got them into the backbox, I used an IDC punchdown tool to punch the white with black wire into connector J122, pin 1 for the green reset coil. I then inserted the bluish green wire for the small yellow coil into connector J130, pin 7.
The process took me about 5 hours total, not including shopping for the parts needed. Shout outs to McCune and PinballHelp for their assistance in this project.