Below is the list of the Hitboxes used by each Car:

Breakout Hitbox
Animus GP
Breakout
Breakout Type S
Cyclone
Komodo 
Samurai

Dominus Hitbox
'70 Dodge Charger R/T
‘89 Batmobile
Aftershock
Chikara/Chikara G1/Chikara GXT
DeLorean
Diestro
Dominus
Dominus GT
Ecto-1 (Ghostbusters)
Gazella GT (Hot Wheels)
Guardian/Guardian G1/Guardian GXT
Hotshot
Ice Charger
Imperator DT5
K.I.T.T. (Knight Rider)
Masamune
Maverick/Maverick G1/Maverick GXT
McLaren 570S
MR11 (Hot Wheels)
Nemesis
Peregrine TT
Ripper
Ronin/Ronin G1/Ronin GXT
Samus’ Gunship (Nintendo Exclusive)
Werewolf

Hybrid Hitbox
Endo
Esper
Jäger 618 RS
Nimbus
‘99 Nissan Skyline GT-R R34
Venom
X-Devil
X-Devil MK2

Merc Hitbox
Merc

Octane Hitbox
Armadillo (Xbox Exclusive)
Backfire
Bone Shaker
Fast 4WD (Hot Wheels)
Fennec
Gizmo
Grog
Hogsticker (Xbox Exclusive)
Jurassic Jeep Wrangler
Luigi NSR (Nintendo Exclusive)
Marauder
Mario NSR (Nintendo Exclusive)
Mudcat/Mudcat G1/Mudcat GXT
Octane
Octane ZSR
Proteus
Road Hog
Road Hog XL
Scarab
Sweet Tooth (PlayStation Exclusive)
Takumi
Takumi RX-T
Triton
The Dark Knight Rises Tumbler
Twinzer
Vulcan
Zippy

Plank Hitbox
‘16 Batmobile
Artemis/Artemis G1/Artemis GXT
Centio
Mantis
Paladin
Sentinel
Twin Mill III