iv only been able to find one thread on this what do i need to change to get the hatch/coupe bumper to fit on a 4 door?

 

That all depends on what your definition of "fit" is. The bumper itself will bolt up on its own with no mods, it will also look like crap cause it doesn't line up with the front fenders properly. To do it right you need to cut and weld coupe/hatch fenders and sedan fenders together and use coupe/hatch corner lights.