changing seatbelts?

so i got these red seat belts out of a ford f-150 and i want to put them in my mustang because the sock belts have gotten caught in the door so many times that their all worn out and falling apart , and i think red would look good with the black seats and soon to be black carpet , i just dont know how to even get to them , any help? it looks tricky
 
Unfortunately, you are better off getting the correct belts for the car.

Seat belts have to mount at a certain angle or they won't work. has to do with the inertial system inside the belt that locks them up. Install at the wrong angle and they might not work in a crash.

So in order to even mount the belts, something will be modified or rigged and trusted to work.