Doing this quick because I have a meeting but this should be all you need if you know how to mod GTAIV. I'm actually surprised I never posted it here. I distinctly remember telling myself I'd do it once I finished the JSPECs and made sure the damage modeling was good but never got around to it. Anyway, video and link/files below.
Email me with any questions as I don't check TT.net often enough. I'm also getting slammed with Back to the Future questions right now so I may take a bit to respond.
"Find out just what any people will quietly submit to and you have the exact measure of the injustice and wrong which will be imposed on them." - Frederick Douglas