I just checked my Max Payne 3 installation and it doens't use any img files at all,
The entrie game is build around .rpf files.
I have a steam install though, but I don't think that a disc install would use other files.
I did find these files:
vehs01.rpf
vehs02.rpf
vehs03.rpf
vehs04.rpf
vehs05.rpf
Which looks like the files for the cars,
But there arn't any handling or ide files with, I could not find any texture files
either. My gues is that you will have to do a MAJOR convert to put them in GTA IV.
The files are about 35MB Each btw.
Let me know if they are useful to you, but my guess it that they aren't,
It looks like they took a completly different aproach on Max Payne.
Kind Regards,
VenomXNL