I recommend ZModeler. Spares yourself convertung work from 3DS Max to ZModeler. Because you can only export IV vehicles with ZModeler. Second, it's not needed to add ELS, you can also create non ELS Mods, like I do.
Just a sample of my work: http://www.lcpdfr.com/files/file/528-liber...pr-fsvr-v11-eg/
Easily added a FS vector Lightbar, made it non ELS, and made the indicators work with the Traffic Advisor. (Yellow strobe on the back of the Lightbar). it's not that hard once you know the basics.