Welcome Adam699...
It looks like you have a wrecked Countach replica and an unmounted replica Countach body. I suppose you want to use the good body to repair the damaged car. You could cut up the good body for parts to fix the damaged BUT I'm sure they are not of the same manufacture and so may not match perfectly. Still it could be done.
It appears the yellow car has a shorter wheelbase than the body and, as we can all see, it is a roadster, not a coupe. There were some kits made to fit the Fiero's original wheelbase. That appears to be the yellow car. (A little hard to tell for sure.)
The yellow car is lacking a lot of authenticity, and so just resembles a Lambo. The body looks pretty good.
In my opinion, replacing the entire yellow body with the complete coupe body would make a nicer car BUT it would take a LOT of work to do so.
If you are inexperienced, believe me, you are in for a really big task.
To me, it seems a shame to cut up the good body even though it may be the easiest way for you to make the car whole.
In any case this is the site you need for advice.
Good luck and please let us know what you intend to do before you start cutting.
