I recall something about a TOW missile being fired off a car. Are you sure?
And here's one idea if you can't find anything...
Use one of these:
BAS OFPR BRDM with MG and add missiles via addweapon. (I've added missiles & rockets to M2s before ;D)
OR
use the mg on a car script in the ed depot and add roackets to that if possible.
Maybe that'll work if the MCAR doesn't do what you want.