The Savanna from GTA SA with ALL tuning parts included and fully usable, along with all liveries. Fits best into IV:SA.
I've included the .max project file for anyone who wants to make their own fully tunable car.

REQUIRES v65.0 or newer of Zolika1351's Trainer/Mod Menu to work, otherwise the car is completely unusable. v65.5 or newer recommended to avoid instability and to be able to purchase tuning parts in Pay 'n' Sprays (Vehicle Options - Pay 'n' Spray Mod Garages)
PUT SAVANNA.DAT INTO THE "carmods" FOLDER! (if it doesn't exist, create a folder called "carmods" in your game folder and put the .dat there)

Vehicles.ide:
savanna, savanna, car, FELTZER, FELTZER, VEH@STD, NULL, 100, 999, 0.2660, 0.2660, 0, 5, 1.0 ,0, ext_conv+livery
txdp
vehshareSA, vehshare
savanna, vehshareSA

Carcols.dat:
savanna, 0,0,49, 38,38,85, 0,97,102, 3,0,12, 6,6,4, 11,4,12, 13,13,12, 16,95,90, 24,1,12, 21,21,12, 23,23,2, 31,31,27, 32,113,34, 34,12,34, 49,13,41, 52,0,59, 62,13,69, 76,4,76, 82,85,76, 87,8,76, 89,0,4, 92,95,90, 95,95,2, 106,103,2,

Tuning part count: 12
Tuning part list:
Stock Front Bumper
Chromer Bumper
Slamin Bumper
Stock Rear Bumper
Chromer Bumper
Slamin Bumper
Hardtop
Softtop
Chrome Strips
Stock Exhaust
Chromer Exhaust
Slamin Exhaust