78 mustang II
 

I have a '78 mustang II. I am currently restoring the car for a daily driver. Is a carpet kit for the car a good idea or is is better to use a big piece and cut it your self?

Definitely go with the carpet kit. Unless you have the patience of Job forget trying to make a flat piece of carpet fit into that floor. Even the kit, which is pre-molded will take some time to lay down right.