To install you need OpenIV, then just open vehicles.img and make sure you are on edit mode and then drag and drop the files in there.
Then open handling.dat and find Futo and change the line to:

FUTO 690.0 0.60 88 0.0 0.134 -0.5 0.00 5 0.188 1.0 172.0 0.21 0.642 0.50 32.0 1.32 1.12 14.0 0.15 0.4800 2.2 1.4 1.4 0.10 -0.15 0.00 0.52 1.0 0.6 1.1 1.5 0.0 14000 440000 0 0

Optionally you can use the Pena/Green car skin instead of having the car with random colors.

Enjoy.

Credits

Amistech Games- for making the car
GTA Mods Del Norte- for porting the car over to SA
CarCrasher730- for porting the car from SA to IV