only way your going to "compromise safety" is if you run a slick in the rain or run old/wore out tire. Almost anything else is an upgrade. As far as size something you'll learn is we push the boundries from stock, guys are up to 20" rims, thousands of hp, super fast, super low. So when you say "without compromising safety, handling, and design limitations?" your just saying what is stock. Your not after stock as you stated, you want to be different. So that means you set a goal and make it happen, either you learn, you pay, or you dont.
Before you buy a car you need to list out what it needs to do (10/15/20/25mpg?, pump gas, breaks in to the 14/13/12/11/10/9's at the strip, autoX) and what you dont want it to do (loud, lots of maintenance, whatever)
yea slant six dan is against it if its not stock, where as running a 2.25" exh into a DRONE FREE flowmaster super 50 Delta and 2.25 or 2.5" to the bumper will net more gains.
make your list before you drop a cent and then pick the car and build it that way. FYI the cost of a more door vs 68 Dart 270 is nothing, they cost the same to register and insure...