I think its a lot easier to photoshop than it is pull off in real life. A top chop on a sedan would be monsterous amount of work to get done right...I'm not saying it couldnt be done, but making it look like the pic would be an incredible task.
Do some comparisons between auto concept art and what the actual vehicles turned out to be...not just production cars but some of Foose's creations as well.
Dont get me wrong, the pic looks hot, but door geometry and window angles would be real mother.
Fender flares and fat meats might be hard on hubs but much easier to make look right.
...and I love that pace car btw...even though it has no functioning roof. Here's a pic I chopped some time ago with larger chrome wheels and an oversized spoiler.