This is my first successful attempt at a vehicle envelope. This pack includes 2 helicopters from GTA IV - Maverick and Police Maverick. The models look good in the game, no bugs were found.
The author of the original envelope in GTA SA is CobriTO.
Installation: Throw vehicles.col in the modelscoll along the way. Open gta3.img with any IMG editor (for example, IMG Tool), find and replace files with their analogues, located in the archive.