How to 
1)Add track to game

Create directory a198 in gpl/track directory 
copy all files any tracks and paste to a198 dir.
rename *.dat file a198.dat
copy 
a198.3do
a198.trk
track.ini
all *.mip file
to a198 dir.

3) edit season.ini in season dir

[EventXX]
name=Austria historic GP
shortname=A 1 ring
trackDirectory=a198
month=7
day=26
numberOfLaps=82
startingGrid=10