Maybe this will help someone else.
Here is how I ended up doing it:
This covers all Ford focus hatchbacks ZX3 and ZX5 models from 2000 to 2007 as they use the same taillights.
I used 3 wire trailer style ribbon cable for the taillight harness.
NAPA LS6474 sockets - you can also buy sockets with a grounding tab at pep boys or autozone etc., NAPA used to carry them but the parts counter man could not find one in the catalog. I went with NAPA echlin as I though they were a tiny bit better quality than the ones available in the other stores. I drilled out a small hole next to one of the tabs that hold the socket in place and soldered a ground wire in place. I then soldered the other wires on the two remaining leads and recorded the color coding. Remember when wiring an 1157 bulb the shorter filament is the brake light and turn signal light. The taller filament is the running/park light.
I purchased 2 1157 LED bulbs at pep boys for 10 bucks apiece. Make sure you get red LEDs behind a red lens. You could also use a regular incandescent bulb.
Note of caution: There are three chambers in the taillight, one with silver reflective parabolic dish in it ( this is the one you want and has the factory bulb in it also) The bottom chamber houses the backup light. THe center chamber has a red reflector in it. However tempting, do not drill into this one. I searched forums spec. geared to focus owners and I found out someone else did drill a hole in this chamber and ended up dislodging the reflector and he could not get it back in position. Plus with no silver reflective material on it, it would not be as bright.
Using a 1 1/8 inch hole saw carefully drill out a hole in the plastic taillight next to the other bulb. The 1 1/8 size is for the NAPA socket, others may be different so test run a hole in a piece of scrap wood or plastic. Use slow speed on the drill and take your time. Do not go at an angle.
At this time you might want to wash out the inevitable plastic shavings and let dry inside overnight. A blast from a hairdryer through the holes every now and then helps.
Reinstall light, I did not cut into the rubber grommet that the factory wires pass through instead, I fed the new wires thru between the bottom of the grommet and the metal of the body. I used butyl rubber tape to seal around the whole grommet and the new bulb wires, to keep it watertight.
I fed the passenger side through the body channel under the plastic trim and my terminations are made in the drivers side rear corner and tucked under the carpet.
The 4 wire feed I have routed behind the rear side trim and I removed the door sill cover and fed the wire under the carpet there.
Then on thru the firewall and to the plug to connect up with the MH.
If you can do this when it's not 20 degrees outside