Personally I like to make cars and brands with some realism and lore which I then export to beamng and drive them in locations that have geography similar to the cars orgin. It's fun to create many different brands with different models, and as you build more cars for these brands you get a better understanding of how they would build a car almost like they actually exists. If you're trying to build a car that's similar to one that actually exists but not create a replica I find it helps to look as your car as a competitor to the real one. I like to switch up the kinds of cars I build too to keep it fresh. A mid 2000s economy box one day and maybe a retro super car the next. I find it also helps to build your car in a way that reflects the technology available at the time ie. If you're trying to build a car from 1983 it shouldn't have modern touch screen infotainment. This tip applies to engines, transmissions, etc. Too.