Hi Brian,
I have done this. I used some generic LED's from Jaycar (3 in each solid state unit) and the rest is easy, a constant active is found in the fuse box adjacent to the passengers feet and the earth is from the passenger side door switch, the door switches are closed to earth and as such you will not be able to have the foot lamps operate independently.
HOW TO.
Remove the trim from the passengers rear door pillar to expose the door switch.
Remove the sill trim.
Remove the passenger side kick panel (Carefully so as not to break the push centre clips).
Using a scotch lock type connector join a cable (2.4m) to the one that exits the back of the switch this will be the earth in your circut.
Run the cable along the door sill, behind the kick panel and under the dash to the first lamp position, I mounted mine above the transmission turrent, leave a loop of cable to work with and then continue to the next position, leaving the cable tail.
Locate a constant active in the fuse block above the pasengers feet, there are a number of ways of attaching a cable here, but a piggy back fuse is the easiest (an auto electrician should have one, 3 amp is perfect and it will act as your in line fuse
safety). DO NOT CONNECT THE POWER YET.
Run this cable to the first lamp position, leave a loop to work with and continue on to the second lamp.
Connect your lamps and
if you do use LED's remember that they are polarity sensitive (ie +to+, -to-).I soldered all of my joints but crimping is fine (you can twist and check your circut if you like) ensure that there are no exposed ends, attach the power side open and close both doors to check operation and if all is OK, secure your new cabling out of the way where it cannot rub on anything. leaving the lamps to hang for now.
Refit all of the trim, again making sure that nothing will rub.
Wait until dark and tune the position of the lamps to suit and then secure them into place with a cable tie.
The image show the LED's wired in series but you can just cut them off as required, think about which end you cut so as not to waste the last one, I also installed an extra lamp in my boot, in the centre and above everything.
Greg.
PM me if you get stuck. Oh, and if you are up to it you could also install a lamp into the glove compartment, using the same active, a micro switch (need to drill a hole and a different earth).
I have just re-read your post, If you need a master switch the best placement is in the active side, ie; at the fuse panel but LED current draw is minimal anyway, once you install them you will be shopping for an LED insert for the overhead light just to match the colour
.
My post will be riddled with it.