In LapsFree, you can move the drivers up and down in the "Tables" screen.
The car# refers to the transponder#
It has to be done manually, but that is about the best way to do it with your system.
With the limited numbers you have, the way it is supposed to work is for each driver to use the number assigned by the software. All of the transponders are kept together in the pits and before each race, the drivers check the grid listings, grab the correct transponder and put it in their car. After the race, they return them so the guys in the next race can take them.
Trying to use your TrakMate transponders as "personals" will be troublesome at best.
Craig