When Fiat added the shock absorbing bumpers in '75 they changed the shape of the grille to accommodate the shocks. They put a cutout on the sides. When you do a conversion on a late 1979 -1988 car, you need to get a 1975-1978 grille.
1974 grille shape marked in red
Shape of a 1974 grille marked in red. Like the rust;)
The other difference is the late model cars have these grille support "teeth" hanging down. These have to be removed. Luckily they come off pretty easily. Just grab hold of one (use a glove because the sheet metal can be sharp) and start to wiggle it back and forth and they will eventually cleanly break off. The trick is to start wiggling it with a short motion, and then as the metal gets worked you'll feel it give way and then break.
These need to come off 
Good, now do the rest!
