A "Hemi" is not accurate to this car.
In the 50s, "Hemis" were not the big block high performance engines found in late 60s/70s muscle cars.
They were just better performing engines.
The first Chrysler Hemi offered (in a car) was a V6.
I'm not a huge fan of the Christine movie, but I love movie cars and their history.
So I did a little research.
The engine in the AMT kit looks like a small block V8 (accurate)
however the single air filter housing would be incorrect since it was a twin carb setup.
It should have two oval air cleaners.
In the Stephen King book, Christine was a 1958 Plymouth Fury 4-door.
However, the Fury did not come as a 4-door.
In the film, the car became a 2-door, obviously.
However, of the 24 cars acquired for the movie, only one was a Fury.
The rest were Savoys and Belvederes (pretty much the same car).
Engine options for the 1958 Fury were:
318 twin 4bbl V8,
350 twin 4bbl Golden Commando V8 (popular choice)
or the 350 big block V8 with Electronic Fuel Injection.
The Belvedere (and Savoy) models came with both 6 and 8 cylinder options,
ranging from 230 inline 6 to a 350 V8 with single 4bbl carb.
According to the Peterson Automotive Museum (where the alleged Christine Fury is now)
the engine is the small block 318 V8 with twin 4bbl carbs.
So you should only need to modify the air cleaners.