Hey, I just found this tool out on the web, made by the one and only Alexander Blade!
It allows you to change the sound bank a vehicle uses in GTA SA (like change heli sound to car sound) by modifying the exe. I found this very helpful in BTTFSA, and I'm sure many others will, too. It also changes door sounds, radio, and horn sounds.
Here is the GTAForums topic:
http://gtaforums.com/topic/278125-sa-vehicle-audio-editor/
The download in the GTAF topic is broken, so here's the download:
http://www.gamemodding.net/en/gta-san-andreas/gta-sa-programms/18703-gta-san-andreas-vehicle-audio-editor-rus-eng.html
I made this topic because a few members were wondering how to change sound banks for vehicles in SA a while back. This is the solution.
There's one weird part to this that Alexander Blade did not obviously post. When changing the sound bank, the actual value you input into the program is the sound bank number + 6. So, if you were going to select bank 32, you would input the number 38 instead. Also, you need to save the exe after each change. Otherwise, your changes will be lost.
See you in the future..or in the past...
-BTTFModMachine