This mod lets you to generate list of free IDs (item definition).
Each object, car, building, ped, whatever it is needs to be declared in files of IDE type and takes single ID.
It is especially important to mappers or modders adding vehicles to know what IDs can be used.

I put a list of free IDs generated on unmodified GTA San Andreas too.
GTA San Andreas v1.0 [US] HOODLUM No-CD Fixed EXE and CLEO4 is required for mod to work correctly, otherwise it might crash.
I added original source of this CLEO script.

****** Usage
During the gameplay type "FREE".
Free IDs.txt will be generated in root GTA San Andreas, the same directory where is gta_sa.exe.
Open this file in any of text editors and you can find free IDs (identifiers)