Yes, it's
. You might want to invest in Fire Blast regardless. Arcanine/Growlithe's Special Attack is good, and you won't get Flare Blitz/Flamethrower for quite a while. And if you opt for Flare Blitz, you'll miss out on Extreme Speed (if you don't breed). You'll be able to plow over Pokemon higher levels than you with it.
Thanks to his high speed (and the 30% flinch rate), and need to be able to hit Water types for decent damage he's a good Headbutt Pokemon. If you do equip him with Sunny Day though Fire Blast/Solarbeam combination causes a lot of pain!