Well 1999 B-series would have the cab fuse box on drivers side, in the early 2000's they moved it to passenger side and it was renamed the Smart Junction Box(SJB), they called it this because Ford/Mazda got rid of the GEM(generic electronic module) at that time and combined its function with fuse box, so "Smart" Junction/fuse Box.
Not sure what you are doing with the switches???
The control systems in vehicles made after 1995 use the computer to run pretty much every thing, or a GEM for some things.
For the transmission over drive any switch would be telling the computer to either use OD or not use OD, it won't be connected to the transmission directly.
So a Factory OD switch, would most likely just be a Ground for 1 pin on the computer connector, i.e. if wire/pin is grounded then no OD, if no ground then used OD
They very rarely use 12volts for any controls any more, they send 12volts to everything when key is on but leave it unGrounded so it is OFF, to turn something on they Ground it.
This saves lots of money and is safer than running 12volt wires every where.
And since body and chassis are Grounds you only need 1 control wire for any switch, it is just grounded to cab.
VSS(vehicle speed sensor) can run 2 different ways in your year.
If you have 4 wheel ABS then VSS wire runs to 4WABS module where signal is converted for tire size and rear axle ratio, and then sent out to Speedo/odo, Cruise and computer.
If you have Rear wheel ABS the VSS signal goes to GEM where it is converted for tire size and axle ratio then sent out to Speedo/odo, Cruise and computer.