Ok, some links then
First remove all old content. So, if you have anything related to the Maserati, uninstall it in the mod manager, and delete the components or mods from the package folder.
Then download these 2 files, unzip, and place them in the package folder:
http://www.gamefront.com/files/21677303/MaseratiGT_Cup_rfcmp_v12_zip
http://www.gamefront.com/files/21709052/MaseratiGT_Cup_rfcmp_v13_zip
Now, open the MOD manager
UNtick the Show mods only box
Look for the sound component of the MaseratiGT
Install it
Look for version 1.2 of the Maseratie GT car
Install it.
The * mark should appear before the GT car. Right click it, and select update.
You should have version 1.3 installed now. You can play the offline version via the All cars and tracks series.
If someone could make a decent basic setup for these cars, I would appreciate it, as I can;t do that myself.