you should know how to install cars...
img tool open gta3.img

vehicles.ide
489,	rancher, 	rancher, 	car,		RANCHER, 	RANCHER, 	null,	normal,	10,	0,	,0	-1, 0.87, 0.87,	0

handling.cfg
RANCHER       3000.0 	6000.0 	3.0 	0.0 	0.35 	0.0 	80 	0.78 	0.80 	0.4 	5 	250.0 	30.0 	15.0 	R 	P 	8.5 	0.30 	0 	35.0 	1.0 	0.12 	0.0 	0.24 	-0.20 	0.5 	0.5 	0.44 	0.30 	40000 	220020 	700000 	1 	1 	0 	

carcols - 
any, secondary color is trim, main color is body.

carmods
rancher,  exh_b_ts, exh_b_l,  nto_b_tw, rf_b_sc_r, spl_b_bar_m, spl_b_bbr_m, spl_b_mar_m, spl_c_s_b, spl_a_l_b, spl_c_l_b

OffRoader23 2006