this mod in a boeing vertol h-21 workhorse, it replaces the leviathan in the game, one dff and one txd.
to install it, you just have to:
1) Open the file gta3.img (IMG-Tool)
2) replace leviathn dff and txd
3) replace the leviathn line in vehicle.ide:
417, 	leviathn, 	leviathn, 	heli, 		LEVIATHN, 	LEVIATH, 	null, 	ignore, 		5, 	0, 	0, 		-1, 0.54, 0.54, 		-1
thanks.