>>36281205You can get Larvitar before Kanto in the Safari Zone, but depending on your starting Safari Zone layout, you may need to do the sidequest to customise it first (it only appears in the Mountain habitat).
Getting it to become Tyranitar before the Elite Four will be tricky by virtue of it needing to be Level 55 in a region with an almost non-existent level curve, but it is doable.
As an aside, you can also get the Choice Scarf via random items your mother buys, and if you teach Tyranitar Blizzard and make it hold it, it's a pretty effective Lance killer if you don't have anything else that can outspeed/one-shot Dragonite.
