When you are ready to put a converted car into Viper Racing and have all your car files
in a folder ready to mkres together,do the following first.

To put an "aero kit" option in the Garage/Aero tab section of the Viper Racing game,
replace a hex entry after you convert your "carname.txt" to a "carname.cf" file.
The "carname"word shown here is actually the name of your car.
Using a hex editor open your "carname.cf" file and replace this hex string:

CD CC CC 3D CD CC CC 3D 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

YOU CAN COPY AND PASTE THIS LINE OF NUMBERS IN THE CORRECT PLACE IN YOUR HEX EDITOR:
CD CC CC 3D CD CC CC 3D 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Replace the hex string above with the hex string below:

B8 1E 05 3E B8 1E 06 3E 6F 12 83 BA 6F 12 83 BA 66 66 66 BF 66 66 66 BF

YOU CAN COPY AND PASTE THIS LINE OF NUMBERS IN THE CORRECT PLACE IN YOUR HEX EDITOR:
B8 1E 05 3E B8 1E 06 3E 6F 12 83 BA 6F 12 83 BA 66 66 66 BF 66 66 66 BF

Here is how to do the steps mentioned above....

Close and save the cf file.
Now mkres the car together and you're done!